ASoC: stm32: add bindings for SAI

STMicroelectronics STM32 Serial Audio Interface (SAI).

The SAI interface (Serial Audio Interface) offers a wide set of audio protocols

as I2S standards, LSB or MSB-justified, PCM/DSP, TDM, and AC'97.

The SAI contains two independent audio sub-blocks. Each sub-block has

its own clock generator and I/O lines controller.

Required properties:

  - compatible: Should be "st,stm32f4-sai"

  - reg: Base address and size of SAI common register set.

  - clocks: Must contain phandle and clock specifier pairs for each entry

	in clock-names.

  - clock-names: Must contain "x8k" and "x11k"

	"x8k": SAI parent clock for sampling rates multiple of 8kHz.

	"x11k": SAI parent clock for sampling rates multiple of 11.025kHz.

  - interrupts: cpu DAI interrupt line shared by SAI sub-blocks

Optional properties:

  - resets: Reference to a reset controller asserting the SAI

SAI subnodes:

Two subnodes corresponding to SAI sub-block instances A et B can be defined.

Subnode can be omitted for unsused sub-block.

SAI subnodes required properties:

  - compatible: Should be "st,stm32-sai-sub-a" or "st,stm32-sai-sub-b"

	for SAI sub-block A or B respectively.

  - reg: Base address and size of SAI sub-block register set.

  - clocks: Must contain one phandle and clock specifier pair

	for sai_ck which feeds the internal clock generator.

  - clock-names: Must contain "sai_ck".

  - dmas: see Documentation/devicetree/bindings/dma/stm32-dma.txt

  - dma-names: identifier string for each DMA request line

	"tx": if sai sub-block is configured as playback DAI

	"rx": if sai sub-block is configured as capture DAI

  - pinctrl-names: should contain only value "default"

  - pinctrl-0: see Documentation/devicetree/bindings/pinctrl/pinctrl-stm32.txt

Example:

sound_card {

	compatible = "audio-graph-card";

	dais = <&sai1b_port>;

};

sai1: sai1@40015800 {

	compatible = "st,stm32f4-sai";

	#address-cells = <1>;

	#size-cells = <1>;

	ranges;

	reg = <0x40015800 0x4>;

	clocks = <&rcc 1 CLK_SAIQ_PDIV>, <&rcc 1 CLK_I2SQ_PDIV>;

	clock-names = "x8k", "x11k";

	interrupts = <87>;

	sai1b: audio-controller@40015824 {

		#sound-dai-cells = <0>;

		compatible = "st,stm32-sai-sub-b";

		reg = <0x40015824 0x1C>;

		clocks = <&rcc 1 CLK_SAI2>;

		clock-names = "sai_ck";

		dmas = <&dma2 5 0 0x400 0x0>;

		dma-names = "tx";

		pinctrl-names = "default";

		pinctrl-0 = <&pinctrl_sai1b>;

		ports {

			#address-cells = <1>;

			#size-cells = <0>;

			sai1b_port: port@0 {

				reg = <0>;

				cpu_endpoint: endpoint {

					remote-endpoint = <&codec_endpoint>;

					audio-graph-card,format = "i2s";

					audio-graph-card,bitclock-master = <&codec_endpoint>;

					audio-graph-card,frame-master = <&codec_endpoint>;

				};

			};

		};

	};

};

audio-codec {

	codec_port: port {

		codec_endpoint: endpoint {

			remote-endpoint = <&cpu_endpoint>;

		};

	};

};