ASoC: dt-bindings: codecs: Add bindings for nxp, tfa989x

NXP/Goodix TFA989X (TFA1) amplifiers are controlled via an I2C bus.
Add simple device tree bindings that describe how to set them up
in the device tree.

Right now only nxp,tfa9895 is supported but this will be extended
to at least nxp,tfa9897 in the near future.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210513104129.36583-1-stephan@gerhold.netSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/nxp,tfa989x.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/nxp,tfa989x.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP/Goodix TFA989X (TFA1) Audio Amplifiers
+
+maintainers:
+  - Stephan Gerhold <stephan@gerhold.net>
+
+properties:
+  compatible:
+    enum:
+      - nxp,tfa9895
+
+  reg:
+    maxItems: 1
+
+  '#sound-dai-cells':
+    const: 0
+
+  sound-name-prefix:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      Used as prefix for sink/source names of the component. Must be a
+      unique string among multiple instances of the same component.
+
+required:
+  - compatible
+  - reg
+  - '#sound-dai-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      audio-codec@34 {
+        compatible = "nxp,tfa9895";
+        reg = <0x34>;
+        sound-name-prefix = "Speaker Left";
+        #sound-dai-cells = <0>;
+      };
+      audio-codec@36 {
+        compatible = "nxp,tfa9895";
+        reg = <0x36>;
+        sound-name-prefix = "Speaker Right";
+        #sound-dai-cells = <0>;
+      };
+    };