dt-bindings: phy: mvebu-utmi: add UTMI PHY bindings

Add bindings for Marvell Armada 3700 USB2 UTMI+ PHY.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/phy/phy-mvebu-utmi.txt

+MVEBU A3700 UTMI PHY
+--------------------
+
+USB2 UTMI+ PHY controllers can be found on the following Marvell MVEBU SoCs:
+* Armada 3700
+
+On Armada 3700, there are two USB controllers, one is compatible with the USB2
+and USB3 specifications and supports OTG. The other one is USB2 compliant and
+only supports host mode. Both of these controllers come with a slightly
+different UTMI PHY.
+
+Required Properties:
+
+- compatible: Should be one of:
+	      * "marvell,a3700-utmi-host-phy" for the PHY connected to
+	        the USB2 host-only controller.
+	      * "marvell,a3700-utmi-otg-phy" for the PHY connected to
+	        the USB3 and USB2 OTG capable controller.
+- reg: PHY IP register range.
+- marvell,usb-misc-reg: handle on the "USB miscellaneous registers" shared
+			region covering registers related to both the host
+			controller and the PHY.
+- #phy-cells: Standard property (Documentation: phy-bindings.txt) Should be 0.
+
+
+Example:
+
+	usb2_utmi_host_phy: phy@5f000 {
+		compatible = "marvell,armada-3700-utmi-host-phy";
+		reg = <0x5f000 0x800>;
+		marvell,usb-misc-reg = <&usb2_syscon>;
+		#phy-cells = <0>;
+	};
+
+	usb2_syscon: system-controller@5f800 {
+		compatible = "marvell,armada-3700-usb2-host-misc", "syscon";
+		reg = <0x5f800 0x800>;
+	};