dt-bindings: connector: usb: add altmodes description

Add description of the USB-C AltModes supported on the particular USB-C
connector. This is required for devices like Qualcomm Robotics RB5,
which have no other way to express alternative modes supported by the
hardware platform.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20231204020303.2287338-2-dmitry.baryshkov@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/connector/usb-connector.yaml

@@ -171,6 +171,32 @@ properties:
       offer the power, Capability Mismatch is set. Required for power sink and
       power dual role.
 
+  altmodes:
+    type: object
+    description: List of Alternative Modes supported by the schematics on the
+      particular device. This is only necessary if there are no other means to
+      discover supported alternative modes (e.g. through the UCSI firmware
+      interface).
+
+    additionalProperties: false
+
+    patternProperties:
+      "^(displayport)$":
+        type: object
+        description:
+          A single USB-C Alternative Mode as supported by the USB-C connector logic.
+
+        additionalProperties: false
+
+        properties:
+          svid:
+            $ref: /schemas/types.yaml#/definitions/uint16
+            description: Unique value assigned by USB-IF to the Vendor / AltMode.
+            enum: [ 0xff01 ]
+          vdo:
+            $ref: /schemas/types.yaml#/definitions/uint32
+            description: VDO returned by Discover Modes USB PD command.
+
   port:
     $ref: /schemas/graph.yaml#/properties/port
     description: OF graph bindings modeling a data bus to the connector, e.g.
@@ -289,6 +315,13 @@ examples:
             compatible = "usb-c-connector";
             label = "USB-C";
 
+            altmodes {
+                displayport {
+                    svid = /bits/ 16 <0xff01>;
+                    vdo = <0x00001c46>;
+                };
+            };
+
             ports {
                 #address-cells = <1>;
                 #size-cells = <0>;