ASoC: dt-bindings: Add schema for "awinic,aw8738"

Add a DT schema for describing Awinic AW8738 audio amplifiers. They are
fairly simple and controlled using a single GPIO. The number of pulses
during power up selects one of a few pre-defined operation modes. This
can be used to configure the speaker-guard function (primarily the
power limit for the amplifier).
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20220304102452.26856-2-stephan@gerhold.netSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/awinic,aw8738.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sound/awinic,aw8738.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Awinic AW8738 Audio Amplifier
+
+maintainers:
+  - Stephan Gerhold <stephan@gerhold.net>
+
+description:
+  The Awinic AW8738 is a simple audio amplifier with different operation modes
+  (set using one-wire pulse control). The mode configures the speaker-guard
+  function (primarily the power limit for the amplifier).
+
+allOf:
+  - $ref: name-prefix.yaml#
+
+properties:
+  compatible:
+    const: awinic,aw8738
+
+  mode-gpios:
+    description:
+      GPIO used for one-wire pulse control. The pin is typically called SHDN
+      (active-low), but this is misleading since it is actually more than
+      just a simple shutdown/enable control.
+    maxItems: 1
+
+  awinic,mode:
+    description: Operation mode (number of pulses for one-wire pulse control)
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 7
+
+  sound-name-prefix: true
+
+required:
+  - compatible
+  - mode-gpios
+  - awinic,mode
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    audio-amplifier {
+        compatible = "awinic,aw8738";
+        mode-gpios = <&msmgpio 114 GPIO_ACTIVE_HIGH>;
+        awinic,mode = <5>;
+        sound-name-prefix = "Speaker Amp";
+    };