ASoC: dt-bindings: imx-card: Add binding doc for imx sound card

Imx-card is a new added machine driver for supporting
ak4458/ak5558/ak5552/ak4497 codec on i.MX platforms. But these
DAC/ADCs are not only supported codecs. This machine driver is
designed to be a more common machine driver for i.MX platform,
it can support widely cpu dai interface and codec dai interface.
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1621247488-21412-1-git-send-email-shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/imx-audio-card.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/imx-audio-card.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP i.MX audio sound card.
+
+maintainers:
+  - Shengjiu Wang <shengjiu.wang@nxp.com>
+
+properties:
+  compatible:
+    enum:
+      - fsl,imx-audio-card
+
+  model:
+    $ref: /schemas/types.yaml#/definitions/string
+    description: User specified audio sound card name
+
+  audio-routing:
+    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+    description:
+      A list of the connections between audio components. Each entry is a
+      pair of strings, the first being the connection's sink, the second
+      being the connection's source. Valid names could be power supplies,
+      MicBias of codec and the jacks on the board.
+
+patternProperties:
+  ".*-dai-link$":
+    description:
+      Each subnode represents a dai link. Subnodes of each dai links would be
+      cpu/codec dais.
+
+    type: object
+
+    properties:
+      link-name:
+        description: Indicates dai-link name and PCM stream name.
+        $ref: /schemas/types.yaml#/definitions/string
+        maxItems: 1
+
+      format:
+        description: audio format.
+        items:
+          enum:
+            - i2s
+            - dsp_b
+
+      dai-tdm-slot-num:
+        description: see tdm-slot.txt.
+        $ref: /schemas/types.yaml#/definitions/uint32
+
+      dai-tdm-slot-width:
+        description: see tdm-slot.txt.
+        $ref: /schemas/types.yaml#/definitions/uint32
+
+      cpu:
+        description: Holds subnode which indicates cpu dai.
+        type: object
+        properties:
+          sound-dai: true
+
+      codec:
+        description: Holds subnode which indicates codec dai.
+        type: object
+        properties:
+          sound-dai: true
+
+      fsl,mclk-equal-bclk:
+        description: Indicates mclk can be equal to bclk, especially for sai interface
+        $ref: /schemas/types.yaml#/definitions/flag
+
+    required:
+      - link-name
+      - cpu
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - model
+
+additionalProperties: false
+
+examples:
+  - |
+    sound-ak4458 {
+        compatible = "fsl,imx-audio-card";
+        model = "ak4458-audio";
+        pri-dai-link {
+            link-name = "akcodec";
+            format = "i2s";
+            fsl,mclk-equal-bclk;
+            cpu {
+                 sound-dai = <&sai1>;
+            };
+            codec {
+                 sound-dai = <&ak4458_1>, <&ak4458_2>;
+            };
+        };
+        fe-dai-link {
+            link-name = "HiFi-ASRC-FE";
+            format = "i2s";
+            cpu {
+                sound-dai = <&easrc>;
+            };
+        };
+        be-dai-link {
+            link-name = "HiFi-ASRC-BE";
+            format = "dsp_b";
+            dai-tdm-slot-num = <8>;
+            dai-tdm-slot-width = <32>;
+            fsl,mclk-equal-bclk;
+            cpu {
+                sound-dai = <&sai1>;
+            };
+            codec {
+                sound-dai = <&ak4458_1>, <&ak4458_2>;
+            };
+        };
+    };