dt-bindings: sound: rockchip: Add binding for Audio PWM

Change-Id: Ia7d8bf6e697fbb9ff7de9c0572f9c679136be47c
Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>

Documentation/devicetree/bindings/sound/rockchip,audio-pwm.txt

@@ -0,0 +1,40 @@
+* Rockchip Audio PWM controller
+
+Required properties:
+
+- compatible: "rockchip,audio-pwm-v1"
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- dmas: DMA specifiers for tx dma. See the DMA client binding,
+	Documentation/devicetree/bindings/dma/dma.txt
+- dma-names: should include "tx".
+- clocks: a list of phandle + clock-specifer pairs, one for each entry in clock-names.
+- clock-names: should contain following:
+   - "clk" : clock for Audio PWM controller
+   - "hclk": clock for AHB BUS
+- pinctrl-names: Must contain a "default" entry.
+- pinctrl-N: One property must exist for each entry in
+	     pinctrl-names. See ../pinctrl/pinctrl-bindings.txt
+	     for details of the property values.
+
+Optional properties:
+
+- rockchip,sample-width-bits: Output sampling data width,the value ranges from 8 to 11 bits.
+- rockchip,interpolat-points-cfg: Interpolation rate,the value must be 1/3/7/15 points,
+  if this is set,the linear interpolation mode will be turned on.
+
+Example for Audio PWM controller:
+
+audpwm: audpwm@ff840000 {
+	compatible = "rockchip,audio-pwm-v1";
+	reg = <0xff840000 0x1000>;
+	clocks = <&cru SCLK_AUDPWM>, <&cru HCLK_AUDPWM>;
+	clock-names = "clk", "hclk";
+	dmas = <&dmac 26>;
+	dma-names = "tx";
+	pinctrl-names = "default";
+	pinctrl-0 = <&audpwmm0_pins>;
+	rockchip,sample-width-bits = <11>;
+	rockchip,interpolat-points = <1>;
+	status = "disabled";
+};