dt-bindings: usb: add documentation for typec port controller(TCPCI)

TCPCI stands for typec port controller interface, its implementation
has full typec port control with power delivery support, it's a
standard i2c slave with GPIO input as irq interface, detail see spec
"Universal Serial Bus Type-C Port Controller Interface Specification
Revision 1.0, Version 1.1"

Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Li Jun <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/typec-tcpci.txt

···
+TCPCI(Typec port cotroller interface) binding
+---------------------------------------------
+
+Required properties:
+- compatible:       should be set one of following:
+		    - "nxp,ptn5110" for NXP USB PD TCPC PHY IC ptn5110.
+
+- reg:              the i2c slave address of typec port controller device.
+- interrupt-parent: the phandle to the interrupt controller which provides
+                    the interrupt.
+- interrupts:       interrupt specification for tcpci alert.
+
+Required sub-node:
+- connector: The "usb-c-connector" attached to the tcpci chip, the bindings
+  of connector node are specified in
+  Documentation/devicetree/bindings/connector/usb-connector.txt
+
+Example:
+
+ptn5110@50 {
+	compatible = "nxp,ptn5110";
+	reg = <0x50>;
+	interrupt-parent = <&gpio3>;
+	interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
+
+	usb_con: connector {
+		compatible = "usb-c-connector";
+		label = "USB-C";
+		data-role = "dual";
+		power-role = "dual";
+		try-power-role = "sink";
+		source-pdos = <PDO_FIXED(5000, 2000, PDO_FIXED_USB_COMM)>;
+		sink-pdos = <PDO_FIXED(5000, 2000, PDO_FIXED_USB_COMM)
+			     PDO_VAR(5000, 12000, 2000)>;
+		op-sink-microwatt = <10000000>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@1 {
+				reg = <1>;
+				usb_con_ss: endpoint {
+					remote-endpoint = <&usb3_data_ss>;
+				};
+			};
+		};
+	};
+};