dt-bindings: mmc: uniphier-sd: Add socionext,syscon-uhs-mode property

UHS mode control is included in the interface logic represented
by syscon. To refer this, add new property "socionext,syscon-uhs-mode".
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230125010201.28246-2-hayashi.kunihiko@socionext.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/socionext,uniphier-sd.yaml

@@ -55,6 +55,16 @@ properties:
     minItems: 1
     maxItems: 3
 
+  socionext,syscon-uhs-mode:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      - items:
+          - description: phandle to syscon that configures UHS mode
+          - description: ID of SD instance
+    description:
+      A phandle to syscon with one argument that configures UHS mode.
+      The argument is the ID of SD instance.
+
 allOf:
   - $ref: mmc-controller.yaml