Documentation/process: maintainer-soc: clarify submitting patches

Patches for SoCs are expected to be picked up by SoC submaintainers.
The main SoC maintainers should be addressed only in few cases.

Rewrite the section about maintainer handling to document above
expectation.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Reviewed-by: Kevin Hilman <[e-mail]>
Reviewed-by: Bagas Sanjaya <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Cc: Alexandre Belloni <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Kevin Hilman <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Conor Dooley <[e-mail]>
Cc: Heiko Stübner <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnd Bergmann <[e-mail]>

Documentation/process/maintainer-soc.rst

···
 The main SoC tree is housed on git.kernel.org:
   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git/
 
+Maintainers
+-----------
+
 Clearly this is quite a wide range of topics, which no one person, or even
 small group of people are capable of maintaining.  Instead, the SoC subsystem
-is comprised of many submaintainers, each taking care of individual platforms
-and driver subdirectories.
+is comprised of many submaintainers (platform maintainers), each taking care of
+individual platforms and driver subdirectories.
 In this regard, "platform" usually refers to a series of SoCs from a given
 vendor, for example, Nvidia's series of Tegra SoCs.  Many submaintainers operate
 on a vendor level, responsible for multiple product lines.  For several reasons,
···
 
 Most of these submaintainers have their own trees where they stage patches,
 sending pull requests to the main SoC tree.  These trees are usually, but not
-always, listed in MAINTAINERS.  The main SoC maintainers can be reached via the
-alias [e-mail] if there is no platform-specific maintainer, or if they
-are unresponsive.
+always, listed in MAINTAINERS.
 
 What the SoC tree is not, however, is a location for architecture-specific code
 changes.  Each architecture has its own maintainers that are responsible for
 architectural details, CPU errata and the like.
+
+Submitting Patches for Given SoC
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+All typical platform related patches should be sent via SoC submaintainers
+(platform-specific maintainers).  This includes also changes to per-platform or
+shared defconfigs (scripts/get_maintainer.pl might not provide correct
+addresses in such case).
+
+Submitting Patches to the Main SoC Maintainers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The main SoC maintainers can be reached via the alias [e-mail] only in
+following cases:
+
+1. There are no platform-specific maintainers.
+
+2. Platform-specific maintainers are unresponsive.
+
+3. Introducing a completely new SoC platform.  Such new SoC work should be sent
+   first to common mailing lists, pointed out by scripts/get_maintainer.pl, for
+   community review.  After positive community review, work should be sent to
+   [e-mail] in one patchset containing new arch/foo/Kconfig entry, DTS
+   files, MAINTAINERS file entry and optionally initial drivers with their
+   Devicetree bindings.  The MAINTAINERS file entry should list new
+   platform-specific maintainers, who are going to be responsible for handling
+   patches for the platform from now on.
+
+Note that the [e-mail] is usually not the place to discuss the patches,
+thus work sent to this address should be already considered as acceptable by
+the community.
 
 Information for (new) Submaintainers
 ------------------------------------