arm: add documentation describing Marvell families of SoC

As stated in the introduction of the document, the families of ARM
SoCs at Marvell are very complicated, and it is difficult for
newcomers to understand the organization of this SoC family and how it
relates to the Linux kernel support for those hardware platforms.

This document is only at RFC stage for now, it requires reviews and
comments from the Marvell maintainers, the PXA maintainers and the MMP
maintainers. For correctness of course, but also to add any other
information that would be useful. For example, one of the thing that
wasn't clear how to detail in the documentation is how the SoCs relate
to each other in terms of hardware IP blocks. For example, most of the
Kirkwood/Dove/Armada 370-XP/etc. hardware IPs (I2C, SPI, USB, SATA,
etc.) are identical, while the PXA and MMP families are completely
separate.

Signed-off-by: Thomas Petazzoni <[e-mail]>
Cc: Andrew Lunn <[e-mail]>
Cc: Jason Cooper <[e-mail]>
Cc: Gregory Clement <[e-mail]>
Cc: Eric Miao <[e-mail]>
Cc: Russell King <[e-mail]>
Cc: Haojian Zhuang <[e-mail]>
Cc: Nicolas Pitre <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Olof Johansson <[e-mail]>
Cc: Lior Amsalem <[e-mail]>
Cc: Maen Suleiman <[e-mail]>
Cc: Tawfik Bayouk <[e-mail]>
Cc: Shadi Ammouri <[e-mail]>
Cc: Eran Ben-Avi <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>

---
Changes from v3:
* Add Arnd Bergmann Acked-by.

Changes from v2:
* Mention the plat-<foo> directory that each SoC family is using.
* Take into account Eric Miao's comments on the PXA/MMP families: add
PXA21x/PXA25x/PXA26x to the list, mention which processors are
AP+CP or AP only. Clarify the comments on which SoCs were designed
by Intel, which ones were designed by Marvell after the acquisition
of the XScale family.
* Mention long-term plans regarding the support of those SoC
families.

Changes from v1:
* Added publicly available datasheet for the 88F5182 pointed by
Andrew Lunn.
* Added publicly available datasheet for the 88F5281 found with
Google searches
* Mentionned the Feroceon core name where appropriate, and Sheeva
where appropriate
* Fixed the core names for PXA930, PXA935 and PXA955 after comments
from Arnd Bergmann. Wikipedia is mistakenly suggesting that PXA93x
are Sheeva-based, and there isn't much information available on the
web about the 955.

Documentation/arm/Marvell/README

···
+ARM Marvell SoCs
+================
+
+This document lists all the ARM Marvell SoCs that are currently
+supported in mainline by the Linux kernel. As the Marvell families of
+SoCs are large and complex, it is hard to understand where the support
+for a particular SoC is available in the Linux kernel. This document
+tries to help in understanding where those SoCs are supported, and to
+match them with their corresponding public datasheet, when available.
+
+Orion family
+------------
+
+  Flavors:
+        88F5082
+        88F5181
+        88F5181L
+        88F5182
+               Datasheet               : http://www.embeddedarm.com/documentation/third-party/MV88F5182-datasheet.pdf
+               Programmer's User Guide : http://www.embeddedarm.com/documentation/third-party/MV88F5182-opensource-manual.pdf
+               User Manual             : http://www.embeddedarm.com/documentation/third-party/MV88F5182-usermanual.pdf
+        88F5281
+               Datasheet               : http://www.ocmodshop.com/images/reviews/networking/qnap_ts409u/marvel_88f5281_data_sheet.pdf
+        88F6183
+  Core: Feroceon ARMv5 compatible
+  Linux kernel mach directory: arch/arm/mach-orion5x
+  Linux kernel plat directory: arch/arm/plat-orion
+
+Kirkwood family
+---------------
+
+  Flavors:
+        88F6282 a.k.a Armada 300
+                Product Brief  : http://www.marvell.com/embedded-processors/armada-300/assets/armada_310.pdf
+        88F6283 a.k.a Armada 310
+                Product Brief  : http://www.marvell.com/embedded-processors/armada-300/assets/armada_310.pdf
+        88F6190
+                Product Brief  : http://www.marvell.com/embedded-processors/kirkwood/assets/88F6190-003_WEB.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/kirkwood/assets/HW_88F619x_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/kirkwood/assets/FS_88F6180_9x_6281_OpenSource.pdf
+        88F6192
+                Product Brief  : http://www.marvell.com/embedded-processors/kirkwood/assets/88F6192-003_ver1.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/kirkwood/assets/HW_88F619x_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/kirkwood/assets/FS_88F6180_9x_6281_OpenSource.pdf
+        88F6182
+        88F6180
+                Product Brief  : http://www.marvell.com/embedded-processors/kirkwood/assets/88F6180-003_ver1.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/kirkwood/assets/HW_88F6180_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/kirkwood/assets/FS_88F6180_9x_6281_OpenSource.pdf
+        88F6281
+                Product Brief  : http://www.marvell.com/embedded-processors/kirkwood/assets/88F6281-004_ver1.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/kirkwood/assets/HW_88F6281_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/kirkwood/assets/FS_88F6180_9x_6281_OpenSource.pdf
+  Homepage: http://www.marvell.com/embedded-processors/kirkwood/
+  Core: Feroceon ARMv5 compatible
+  Linux kernel mach directory: arch/arm/mach-kirkwood
+  Linux kernel plat directory: arch/arm/plat-orion
+
+Discovery family
+----------------
+
+  Flavors:
+        MV78100
+                Product Brief  : http://www.marvell.com/embedded-processors/discovery-innovation/assets/MV78100-003_WEB.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/discovery-innovation/assets/HW_MV78100_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/discovery-innovation/assets/FS_MV76100_78100_78200_OpenSource.pdf
+        MV78200
+                Product Brief  : http://www.marvell.com/embedded-processors/discovery-innovation/assets/MV78200-002_WEB.pdf
+                Hardware Spec  : http://www.marvell.com/embedded-processors/discovery-innovation/assets/HW_MV78200_OpenSource.pdf
+                Functional Spec: http://www.marvell.com/embedded-processors/discovery-innovation/assets/FS_MV76100_78100_78200_OpenSource.pdf
+        MV76100
+                Not supported by the Linux kernel.
+
+  Core: Feroceon ARMv5 compatible
+
+  Linux kernel mach directory: arch/arm/mach-mv78xx0
+  Linux kernel plat directory: arch/arm/plat-orion
+
+EBU Armada family
+-----------------
+
+  Armada 370 Flavors:
+        88F6710
+        88F6707
+        88F6W11
+
+  Armada XP Flavors:
+        MV78230
+        MV78260
+        MV78460
+
+  Product Brief: http://www.marvell.com/embedded-processors/armada-xp/assets/Marvell-ArmadaXP-SoC-product%20brief.pdf
+  No public datasheet available.
+
+  Core: Sheeva ARMv7 compatible
+
+  Linux kernel mach directory: arch/arm/mach-mvebu
+  Linux kernel plat directory: none
+
+Avanta family
+-------------
+
+  Flavors:
+       88F6510
+       88F6530P
+       88F6550
+       88F6560
+  Homepage     : http://www.marvell.com/broadband/
+  Product Brief: http://www.marvell.com/broadband/assets/Marvell_Avanta_88F6510_305_060-001_product_brief.pdf
+  No public datasheet available.
+
+  Core: ARMv5 compatible
+
+  Linux kernel mach directory: no code in mainline yet, planned for the future
+  Linux kernel plat directory: no code in mainline yet, planned for the future
+
+Dove family (application processor)
+-----------------------------------
+
+  Flavors:
+        88AP510 a.k.a Armada 510
+                Product Brief   : http://www.marvell.com/application-processors/armada-500/assets/Marvell_Armada510_SoC.pdf
+                Hardware Spec   : http://www.marvell.com/application-processors/armada-500/assets/Armada-510-Hardware-Spec.pdf
+                Functional Spec : http://www.marvell.com/application-processors/armada-500/assets/Armada-510-Functional-Spec.pdf
+  Homepage: http://www.marvell.com/application-processors/armada-500/
+  Core: ARMv7 compatible
+  Directory: arch/arm/mach-dove
+
+PXA 2xx/3xx/93x/95x family
+--------------------------
+
+  Flavors:
+        PXA21x, PXA25x, PXA26x
+             Application processor only
+             Core: ARMv5 XScale core
+        PXA270, PXA271, PXA272
+             Product Brief         : http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_pb.pdf
+             Design guide          : http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_design_guide.pdf
+             Developers manual     : http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_dev_man.pdf
+             Specification         : http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_emts.pdf
+             Specification update  : http://www.marvell.com/application-processors/pxa-family/assets/pxa_27x_spec_update.pdf
+             Application processor only
+             Core: ARMv5 XScale core
+        PXA300, PXA310, PXA320
+             PXA 300 Product Brief : http://www.marvell.com/application-processors/pxa-family/assets/PXA300_PB_R4.pdf
+             PXA 310 Product Brief : http://www.marvell.com/application-processors/pxa-family/assets/PXA310_PB_R4.pdf
+             PXA 320 Product Brief : http://www.marvell.com/application-processors/pxa-family/assets/PXA320_PB_R4.pdf
+             Design guide          : http://www.marvell.com/application-processors/pxa-family/assets/PXA3xx_Design_Guide.pdf
+             Developers manual     : http://www.marvell.com/application-processors/pxa-family/assets/PXA3xx_Developers_Manual.zip
+             Specifications        : http://www.marvell.com/application-processors/pxa-family/assets/PXA3xx_EMTS.pdf
+             Specification Update  : http://www.marvell.com/application-processors/pxa-family/assets/PXA3xx_Spec_Update.zip
+             Reference Manual      : http://www.marvell.com/application-processors/pxa-family/assets/PXA3xx_TavorP_BootROM_Ref_Manual.pdf
+             Application processor only
+             Core: ARMv5 XScale core
+        PXA930, PXA935
+             Application processor with Communication processor
+             Core: ARMv5 XScale core
+        PXA955
+             Application processor with Communication processor
+             Core: ARMv7 compatible Sheeva PJ4 core
+
+   Comments:
+
+    * This line of SoCs originates from the XScale family developed by
+      Intel and acquired by Marvell in ~2006. The PXA21x, PXA25x,
+      PXA26x, PXA27x, PXA3xx and PXA93x were developed by Intel, while
+      the later PXA95x were developed by Marvell.
+
+    * Due to their XScale origin, these SoCs have virtually nothing in
+      common with the other (Kirkwood, Dove, etc.) families of Marvell
+      SoCs, except with the MMP/MMP2 family of SoCs.
+
+   Linux kernel mach directory: arch/arm/mach-pxa
+   Linux kernel plat directory: arch/arm/plat-pxa
+
+MMP/MMP2 family (communication processor)
+-----------------------------------------
+
+   Flavors:
+        PXA168, a.k.a Armada 168
+             Homepage             : http://www.marvell.com/application-processors/armada-100/armada-168.jsp
+             Product brief        : http://www.marvell.com/application-processors/armada-100/assets/pxa_168_pb.pdf
+             Hardware manual      : http://www.marvell.com/application-processors/armada-100/assets/armada_16x_datasheet.pdf
+             Software manual      : http://www.marvell.com/application-processors/armada-100/assets/armada_16x_software_manual.pdf
+             Specification update : http://www.marvell.com/application-processors/armada-100/assets/ARMADA16x_Spec_update.pdf
+             Boot ROM manual      : http://www.marvell.com/application-processors/armada-100/assets/armada_16x_ref_manual.pdf
+             App node package     : http://www.marvell.com/application-processors/armada-100/assets/armada_16x_app_note_package.pdf
+             Application processor only
+             Core: ARMv5 compatible Marvell PJ1 (Mohawk)
+        PXA910
+             Homepage             : http://www.marvell.com/communication-processors/pxa910/
+             Product Brief        : http://www.marvell.com/communication-processors/pxa910/assets/Marvell_PXA910_Platform-001_PB_final.pdf
+             Application processor with Communication processor
+             Core: ARMv5 compatible Marvell PJ1 (Mohawk)
+        MMP2, a.k.a Armada 610
+             Product Brief        : http://www.marvell.com/application-processors/armada-600/assets/armada610_pb.pdf
+             Application processor only
+             Core: ARMv7 compatible Sheeva PJ4 core
+
+   Comments:
+
+    * This line of SoCs originates from the XScale family developed by
+      Intel and acquired by Marvell in ~2006. All the processors of
+      this MMP/MMP2 family were developed by Marvell.
+
+    * Due to their XScale origin, these SoCs have virtually nothing in
+      common with the other (Kirkwood, Dove, etc.) families of Marvell
+      SoCs, except with the PXA family of SoCs listed above.
+
+   Linux kernel mach directory: arch/arm/mach-mmp
+   Linux kernel plat directory: arch/arm/plat-pxa
+
+Long-term plans
+---------------
+
+ * Unify the mach-dove/, mach-mv78xx0/, mach-orion5x/ and
+   mach-kirkwood/ into the mach-mvebu/ to support all SoCs from the
+   Marvell EBU (Engineering Business Unit) in a single mach-<foo>
+   directory. The plat-orion/ would therefore disappear.
+
+ * Unify the mach-mmp/ and mach-pxa/ into the same mach-pxa
+   directory. The plat-pxa/ would therefore disappear.
+
+Credits
+-------
+
+ Maen Suleiman <[e-mail]>
+ Lior Amsalem <[e-mail]>
+ Thomas Petazzoni <[e-mail]>
+ Andrew Lunn <[e-mail]>
+ Nicolas Pitre <[e-mail]>
+ Eric Miao <[e-mail]>