mmc: dt-bindings: add MMC support to JZ4740 SoC

Add the devicetree binding for JZ4740/JZ4780 SoC MMC/SD controller.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.co.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/jz4740.txt

+* Ingenic JZ47xx MMC controllers
+
+This file documents the device tree properties used for the MMC controller in
+Ingenic JZ4740/JZ4780 SoCs. These are in addition to the core MMC properties
+described in mmc.txt.
+
+Required properties:
+- compatible: Should be one of the following:
+  - "ingenic,jz4740-mmc" for the JZ4740
+  - "ingenic,jz4780-mmc" for the JZ4780
+- reg: Should contain the MMC controller registers location and length.
+- interrupts: Should contain the interrupt specifier of the MMC controller.
+- clocks: Clock for the MMC controller.
+
+Optional properties:
+- dmas: List of DMA specifiers with the controller specific format
+        as described in the generic DMA client binding. A tx and rx
+        specifier is required.
+- dma-names: RX and TX  DMA request names.
+        Should be "rx" and "tx", in that order.
+
+For additional details on DMA client bindings see ../dma/dma.txt.
+
+Example:
+
+mmc0: mmc@13450000 {
+	compatible = "ingenic,jz4780-mmc";
+	reg = <0x13450000 0x1000>;
+
+	interrupt-parent = <&intc>;
+	interrupts = <37>;
+
+	clocks = <&cgu JZ4780_CLK_MSC0>;
+	clock-names = "mmc";
+
+	dmas = <&dma JZ4780_DMA_MSC0_RX 0xffffffff>, <&dma JZ4780_DMA_MSC0_TX 0xffffffff>;
+	dma-names = "rx", "tx";
+};