ASoC: dt-bindings: mediatek,mt8188-mt6359: Add mediatek,adsp property

On some MediaTek SoCs, an Audio DSP (ADSP) is integrated as a separate
hardware block that leverages Sound Open Firmware (SOF) and provides
additional audio functionalities. This hardware is optional, and the
audio subsystem will still function normally when it's not present.

To enable ADSP support, a 'mediatek,adsp' property is required in the
sound card node to pass the ADSP phandle. This allows AFE to link to
ADSP when the sound card is probed.

MT8188 has ADSP integrated, so add the 'mediatek,adsp' property to
allow using it in the audio subsystem.

This fixes dtbs_check error:
  Unevaluated properties are not allowed ('mediatek,adsp' was
  unexpected)

Signed-off-by: Fei Shao <[email protected]>
Reviewed-by: Rob Herring (Arm) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Fei Shao

Documentation/devicetree/bindings/sound/mediatek,mt8188-mt6359.yaml

@@ -29,6 +29,13 @@ properties:
     $ref: /schemas/types.yaml#/definitions/phandle
     description: The phandle of MT8188 ASoC platform.
 
+  mediatek,adsp:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      The phandle of the MT8188 ADSP platform, which is the optional Audio DSP
+      hardware that provides additional audio functionalities if present.
+      The AFE will link to ADSP when the phandle is provided.
+
 patternProperties:
   "^dai-link-[0-9]+$":
     type: object