ASoC: meson: add axg sound card DT bindings documentation

Amlogic AXG sound card:

Required properties:

- compatible: "amlogic,axg-sound-card"

- amlogic,name : User specified audio sound card name, one string

Optional properties:

- amlogic,aux-devs : List of phandles pointing to auxiliary devices

- amlogic,widgets : Please refer to widgets.txt.

- amlogic,routing : A list of the connections between audio components.

Subnodes:

- amlogic,dai-link: Container for dai-link level properties and the

		    CODEC sub-nodes. There should be at least one (and

		    probably) subnode of this type.

Required dai-link properties:

- sound-dai: phandle and port of the CPU DAI.

Required TDM Backend dai-link properties:

- dai-format : CPU/CODEC common audio format

Optional TDM Backend dai-link properties:

- dai-tdm-slot-rx-mask-{0,1,2,3}: Receive direction slot masks

- dai-tdm-slot-tx-mask-{0,1,2,3}: Transmit direction slot masks

				  When omitted, mask is assumed to have to no

				  slots. A valid must have at one slot, so at

				  least one these mask should be provided with

				  an enabled slot.

- dai-tdm-slot-num : Please refer to tdm-slot.txt.

		     If omitted, slot number is set to accommodate the largest

		     mask provided.

- dai-tdm-slot-width : Please refer to tdm-slot.txt. default to 32 if omitted.

- mclk-fs : Multiplication factor between stream rate and mclk

Backend dai-link subnodes:

- codec: dai-link representing backend links should have at least one subnode.

	 One subnode for each codec of the dai-link.

	 dai-link representing frontend links have no codec, therefore have no

	 subnodes

Required codec subnodes properties:

- sound-dai: phandle and port of the CODEC DAI.

Optional codec subnodes properties:

- dai-tdm-slot-tx-mask : Please refer to tdm-slot.txt.

- dai-tdm-slot-rx-mask : Please refer to tdm-slot.txt.

Example:

sound {

	compatible = "amlogic,axg-sound-card";

	amlogic,name = "AXG-S420";

	amlogic,aux-devs = <&tdmin_a>, <&tdmout_c>;

	amlogic,widgets = "Line", "Lineout",

			  "Line", "Linein",

			  "Speaker", "Speaker1 Left",

			  "Speaker", "Speaker1 Right";

			  "Speaker", "Speaker2 Left",

			  "Speaker", "Speaker2 Right";

	amlogic,routing = "TDMOUT_C IN 0", "FRDDR_A OUT 2",

			  "SPDIFOUT IN 0", "FRDDR_A OUT 3",

			  "TDM_C Playback", "TDMOUT_C OUT",

			  "TDMIN_A IN 2", "TDM_C Capture",

			  "TDMIN_A IN 5", "TDM_C Loopback",

			  "TODDR_A IN 0", "TDMIN_A OUT",

			  "Lineout", "Lineout AOUTL",

			  "Lineout", "Lineout AOUTR",

			  "Speaker1 Left", "SPK1 OUT_A",

			  "Speaker2 Left", "SPK2 OUT_A",

			  "Speaker1 Right", "SPK1 OUT_B",

			  "Speaker2 Right", "SPK2 OUT_B",

			  "Linein AINL", "Linein",

			  "Linein AINR", "Linein";

	amlogic,dai-link@0 {

		sound-dai = <&frddr_a>;

	};

	amlogic,dai-link@1 {

		sound-dai = <&toddr_a>;

	};

	amlogic,dai-link@2 {

		sound-dai = <&tdmif_c>;

		dai-format = "i2s";

		dai-tdm-slot-tx-mask-2 = <1 1>;

		dai-tdm-slot-tx-mask-3 = <1 1>;

		dai-tdm-slot-rx-mask-1 = <1 1>;

		mclk-fs = <256>;

		codec@0 {

			sound-dai = <&lineout>;

		};

		codec@1 {

			sound-dai = <&speaker_amp1>;

		};

		codec@2 {

			sound-dai = <&speaker_amp2>;

		};

		codec@3 {

			sound-dai = <&linein>;

		};

	};

	amlogic,dai-link@4 {

		sound-dai = <&spdifout>;

		codec {

			sound-dai = <&spdif_dit>;

		};

	};

};