spi/rockchip: add rockchip spi DT binding

Signed-off-by: addy ke <addy.ke@rock-chips.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

Documentation/devicetree/bindings/spi/spi-rockchip.txt

+* Rockchip SPI Controller
+
+The Rockchip SPI controller is used to interface with various devices such as flash
+and display controllers using the SPI communication interface.
+
+Required Properties:
+
+- compatible: should be one of the following.
+    "rockchip,rk3066-spi" for rk3066.
+    "rockchip,rk3188-spi", "rockchip,rk3066-spi" for rk3188.
+    "rockchip,rk3288-spi", "rockchip,rk3066-spi" for rk3288.
+- reg: physical base address of the controller and length of memory mapped
+       region.
+- interrupts: The interrupt number to the cpu. The interrupt specifier format
+              depends on the interrupt controller.
+- clocks: Must contain an entry for each entry in clock-names.
+- clock-names: Shall be "spiclk" for the transfer-clock, and "apb_pclk" for
+			   the peripheral clock.
+- dmas: DMA specifiers for tx and rx dma. See the DMA client binding,
+		Documentation/devicetree/bindings/dma/dma.txt
+- dma-names: DMA request names should include "tx" and "rx" if present.
+- #address-cells: should be 1.
+- #size-cells: should be 0.
+
+Example:
+
+	spi0: spi@ff110000 {
+		compatible = "rockchip,rk3066-spi";
+		reg = <0xff110000 0x1000>;
+		dmas = <&pdma1 11>, <&pdma1 12>;
+		dma-names = "tx", "rx";
+		#address-cells = <1>;
+		#size-cells = <0>;
+		interrupts = <GIC_SPI 44 IRQ_TYPE_LEVEL_HIGH>;
+		clocks = <&cru SCLK_SPI0>, <&cru PCLK_SPI0>;
+		clock-names = "spiclk", "apb_pclk";
+	};