dt-bindings: usb: Document WCD939x USB SubSystem Altmode/Analog Audio Switch

Document the Qualcomm WCD9390/WCD9395 USB SubSystem Altmode/Analog Audio Switch
which is a separate USB SubSystem for Altmode/Analog Audio Switch accessible
over an I2C interface.

Since Audio Headphone and Microphone data path between the Codec and the USB-C Mux
subsystems are external to the IC, it requires a second port to handle USB-C altmode
& orientation switching for Audio Accessory Mode to the Codec SubSystem.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231212-topic-sm8650-upstream-wcd939x-usbss-v2-1-38961fea5867@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/qcom,wcd939x-usbss.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/qcom,wcd939x-usbss.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm WCD9380/WCD9385 USB SubSystem Altmode/Analog Audio Switch
+
+maintainers:
+  - Neil Armstrong <neil.armstrong@linaro.org>
+
+description:
+  Qualcomm WCD9390/WCD9395 is a standalone Hi-Fi audio codec IC with a
+  functionally separate USB SubSystem for Altmode/Analog Audio Switch
+  accessible over an I2C interface.
+  The Audio Headphone and Microphone data path between the Codec and the
+  USB-C Mux subsystems are external to the IC, thus requiring DT port-endpoint
+  graph description to handle USB-C altmode & orientation switching for Audio
+  Accessory Mode.
+
+properties:
+  compatible:
+    oneOf:
+      - const: qcom,wcd9390-usbss
+      - items:
+          - const: qcom,wcd9395-usbss
+          - const: qcom,wcd9390-usbss
+
+  reg:
+    maxItems: 1
+
+  reset-gpios:
+    maxItems: 1
+
+  vdd-supply:
+    description: USBSS VDD power supply
+
+  mode-switch:
+    description: Flag the port as possible handle of altmode switching
+    type: boolean
+
+  orientation-switch:
+    description: Flag the port as possible handler of orientation switching
+    type: boolean
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          A port node to link the WCD939x USB SubSystem to a TypeC controller for the
+          purpose of handling altmode muxing and orientation switching.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          A port node to link the WCD939x USB SubSystem to the Codec SubSystem for the
+          purpose of handling USB-C Audio Accessory Mode muxing and orientation switching.
+
+required:
+  - compatible
+  - reg
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        typec-mux@42 {
+            compatible = "qcom,wcd9390-usbss";
+            reg = <0x42>;
+
+            vdd-supply = <&vreg_bob>;
+
+            mode-switch;
+            orientation-switch;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+                    wcd9390_usbss_sbu: endpoint {
+                        remote-endpoint = <&typec_sbu>;
+                    };
+                };
+                port@1 {
+                    reg = <1>;
+                    wcd9390_usbss_codec: endpoint {
+                        remote-endpoint = <&wcd9390_codec_usbss>;
+                    };
+                };
+            };
+        };
+    };
+...