dt-bindings: usb: musb: Add support for MediaTek musb controller

This adds support for MediaTek musb controller in
host, peripheral and otg mode.
Signed-off-by: Min Guo <min.guo@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bin Liu <b-liu@ti.com>
Link: https://lore.kernel.org/r/20200115132547.364-20-b-liu@ti.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/mediatek,musb.txt

+MediaTek musb DRD/OTG controller
+-------------------------------------------
+
+Required properties:
+ - compatible      : should be one of:
+                     "mediatek,mt2701-musb"
+                     ...
+                     followed by "mediatek,mtk-musb"
+ - reg             : specifies physical base address and size of
+                     the registers
+ - interrupts      : interrupt used by musb controller
+ - interrupt-names : must be "mc"
+ - phys            : PHY specifier for the OTG phy
+ - dr_mode         : should be one of "host", "peripheral" or "otg",
+                     refer to usb/generic.txt
+ - clocks          : a list of phandle + clock-specifier pairs, one for
+                     each entry in clock-names
+ - clock-names     : must contain "main", "mcu", "univpll"
+                     for clocks of controller
+
+Optional properties:
+ - power-domains   : a phandle to USB power domain node to control USB's
+                     MTCMOS
+
+Required child nodes:
+ usb connector node as defined in bindings/connector/usb-connector.txt
+Optional properties:
+ - id-gpios        : input GPIO for USB ID pin.
+ - vbus-gpios      : input GPIO for USB VBUS pin.
+ - vbus-supply     : reference to the VBUS regulator, needed when supports
+                     dual-role mode
+ - usb-role-switch : use USB Role Switch to support dual-role switch, see
+                     usb/generic.txt.
+
+Example:
+
+usb2: usb@11200000 {
+	compatible = "mediatek,mt2701-musb",
+		     "mediatek,mtk-musb";
+	reg = <0 0x11200000 0 0x1000>;
+	interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_LOW>;
+	interrupt-names = "mc";
+	phys = <&u2port2 PHY_TYPE_USB2>;
+	dr_mode = "otg";
+	clocks = <&pericfg CLK_PERI_USB0>,
+		 <&pericfg CLK_PERI_USB0_MCU>,
+		 <&pericfg CLK_PERI_USB_SLV>;
+	clock-names = "main","mcu","univpll";
+	power-domains = <&scpsys MT2701_POWER_DOMAIN_IFR_MSC>;
+	usb-role-switch;
+	connector{
+		compatible = "gpio-usb-b-connector", "usb-b-connector";
+		type = "micro";
+		id-gpios = <&pio 44 GPIO_ACTIVE_HIGH>;
+		vbus-supply = <&usb_vbus>;
+	};
+};