STMicroelectronics STM32 S/PDIF receiver (SPDIFRX).

The SPDIFRX peripheral, is designed to receive an S/PDIF flow compliant with
IEC-60958 and IEC-61937.

Required properties:
  - compatible: should be "st,stm32h7-spdifrx"
  - reg: cpu DAI IP base address and size
  - clocks: must contain an entry for kclk (used as S/PDIF signal reference)
  - clock-names: must contain "kclk"
  - interrupts: cpu DAI interrupt line
  - dmas: DMA specifiers for audio data DMA and iec control flow DMA
    See STM32 DMA bindings, Documentation/devicetree/bindings/dma/st,stm32-dma.yaml
  - dma-names: two dmas have to be defined, "rx" and "rx-ctrl"

Optional properties:
  - resets: Reference to a reset controller asserting the SPDIFRX

The device node should contain one 'port' child node with one child 'endpoint'
node, according to the bindings defined in Documentation/devicetree/bindings/
graph.txt.

Example:
spdifrx: spdifrx@40004000 {
	compatible = "st,stm32h7-spdifrx";
	reg = <0x40004000 0x400>;
	clocks = <&rcc SPDIFRX_CK>;
	clock-names = "kclk";
	interrupts = <97>;
	dmas = <&dmamux1 2 93 0x400 0x0>,
	       <&dmamux1 3 94 0x400 0x0>;
	dma-names = "rx", "rx-ctrl";
	pinctrl-0 = <&spdifrx_pins>;
	pinctrl-names = "default";

	spdifrx_port: port {
		cpu_endpoint: endpoint {
			remote-endpoint = <&codec_endpoint>;
		};
	};
};

spdif_in: spdif-in {
	compatible = "linux,spdif-dir";

	codec_port: port {
		codec_endpoint: endpoint {
			remote-endpoint = <&cpu_endpoint>;
		};
	};
};

soundcard {
	compatible = "audio-graph-card";
	dais = <&spdifrx_port>;
};