dt-bindings: phy: mediatek: tphy: add a property for force-mode switch

Due to some old SoCs with shared t-phy between usb3 and pcie only support
force-mode switch, and shared and non-shared t-phy may exist at the same
time on a SoC, can't use compatible to distinguish between shared and
non-shared t-phy, add a property to supported it.
Currently, only support switch from default pcie mode to usb3 mode.
But now prefer to use "mediatek,syscon-type" on new SoC as far as possible.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231211025624.28991-1-chunfeng.yun@mediatek.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/mediatek,tphy.yaml

@@ -235,6 +235,15 @@ patternProperties:
           Specify the flag to enable BC1.2 if support it
         type: boolean
 
+      mediatek,force-mode:
+        description:
+          The force mode is used to manually switch the shared phy mode between
+          USB3 and PCIe, when USB3 phy type is selected by the consumer, and
+          force-mode is set, will cause phy's power and pipe toggled and force
+          phy as USB3 mode which switched from default PCIe mode. But perfer to
+          use the property "mediatek,syscon-type" for newer SoCs that support it.
+        type: boolean
+
       mediatek,syscon-type:
         $ref: /schemas/types.yaml#/definitions/phandle-array
         maxItems: 1