dt-bindings: Add pxa1928 clock binding

This adds the clock binding documentation for the Marvell PXA1928 SOC.
The PXA1928 has 3 clock control blocks for different subsystems of the
chip.

Signed-off-by: Rob Herring <[e-mail]>
Cc: Pawel Moll <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Ian Campbell <[e-mail]>
Cc: Kumar Gala <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/marvell,pxa1928.txt

···
+* Marvell PXA1928 Clock Controllers
+
+The PXA1928 clock subsystem generates and supplies clock to various
+controllers within the PXA1928 SoC. The PXA1928 contains 3 clock controller
+blocks called APMU, MPMU, and APBC roughly corresponding to internal buses.
+
+Required Properties:
+
+- compatible: should be one of the following.
+  - "marvell,pxa1928-apmu" - APMU controller compatible
+  - "marvell,pxa1928-mpmu" - MPMU controller compatible
+  - "marvell,pxa1928-apbc" - APBC controller compatible
+- reg: physical base address of the clock controller and length of memory mapped
+  region.
+- #clock-cells: should be 1.
+- #reset-cells: should be 1.
+
+Each clock is assigned an identifier and client nodes use the clock controller
+phandle and this identifier to specify the clock which they consume.
+
+All these identifiers can be found in <dt-bindings/clock/marvell,pxa1928.h>.

include/dt-bindings/clock/marvell,pxa1928.h

···
+#ifndef __DTS_MARVELL_PXA1928_CLOCK_H
+#define __DTS_MARVELL_PXA1928_CLOCK_H
+
+/*
+ * Clock ID values here correspond to the control register offset/4.
+ */
+
+/* apb peripherals */
+#define PXA1928_CLK_RTC			0x00
+#define PXA1928_CLK_TWSI0		0x01
+#define PXA1928_CLK_TWSI1		0x02
+#define PXA1928_CLK_TWSI2		0x03
+#define PXA1928_CLK_TWSI3		0x04
+#define PXA1928_CLK_OWIRE		0x05
+#define PXA1928_CLK_KPC			0x06
+#define PXA1928_CLK_TB_ROTARY		0x07
+#define PXA1928_CLK_SW_JTAG		0x08
+#define PXA1928_CLK_TIMER1		0x09
+#define PXA1928_CLK_UART0		0x0b
+#define PXA1928_CLK_UART1		0x0c
+#define PXA1928_CLK_UART2		0x0d
+#define PXA1928_CLK_GPIO		0x0e
+#define PXA1928_CLK_PWM0		0x0f
+#define PXA1928_CLK_PWM1		0x10
+#define PXA1928_CLK_PWM2		0x11
+#define PXA1928_CLK_PWM3		0x12
+#define PXA1928_CLK_SSP0		0x13
+#define PXA1928_CLK_SSP1		0x14
+#define PXA1928_CLK_SSP2		0x15
+
+#define PXA1928_CLK_TWSI4		0x1f
+#define PXA1928_CLK_TWSI5		0x20
+#define PXA1928_CLK_UART3		0x22
+#define PXA1928_CLK_THSENS_GLOB		0x24
+#define PXA1928_CLK_THSENS_CPU		0x26
+#define PXA1928_CLK_THSENS_VPU		0x27
+#define PXA1928_CLK_THSENS_GC		0x28
+#define PXA1928_APBC_NR_CLKS		0x30
+
+
+/* axi peripherals */
+#define PXA1928_CLK_SDH0		0x15
+#define PXA1928_CLK_SDH1		0x16
+#define PXA1928_CLK_USB			0x17
+#define PXA1928_CLK_NAND		0x18
+#define PXA1928_CLK_DMA			0x19
+
+#define PXA1928_CLK_SDH2		0x3a
+#define PXA1928_CLK_SDH3		0x3b
+#define PXA1928_CLK_HSIC		0x3e
+#define PXA1928_CLK_SDH4		0x57
+#define PXA1928_CLK_GC3D		0x5d
+#define PXA1928_CLK_GC2D		0x5f
+
+#define PXA1928_APMU_NR_CLKS		0x60
+
+#endif