dt-bindings: phy: meson-g12a-usb2-phy: convert to yaml

Now that we have the DT validation in place, let's convert the device tree
bindings for the Amlogic G12A USB2 PHY over to a YAML schemas.

While the original phy bindings specifies phy-supply as required,
the examples and implementations makes it optional, thus phy-supply
is not in the required list of attributes.
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: NNeil Armstrong <narmstrong@baylibre.com>
Signed-off-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/amlogic,meson-g12a-usb2-phy.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2019 BayLibre, SAS
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/phy/amlogic,meson-g12a-usb2-phy.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Amlogic G12A USB2 PHY
+
+maintainers:
+  - Neil Armstrong <narmstrong@baylibre.com>
+
+properties:
+  compatible:
+    enum:
+      - amlogic,meson-g12a-usb2-phy
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: xtal
+
+  resets:
+    maxItems: 1
+
+  reset-names:
+    items:
+      - const: phy
+
+  "#phy-cells":
+    const: 0
+
+  phy-supply:
+     maxItems: 1
+     description:
+       Phandle to a regulator that provides power to the PHY. This
+       regulator will be managed during the PHY power on/off sequence.
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - resets
+  - reset-names
+  - "#phy-cells"
+
+examples:
+  - |
+    phy@36000 {
+          compatible = "amlogic,meson-g12a-usb2-phy";
+          reg = <0x36000 0x2000>;
+          clocks = <&xtal>;
+          clock-names = "xtal";
+          resets = <&phy_reset>;
+          reset-names = "phy";
+          #phy-cells = <0>;
+    };

Documentation/devicetree/bindings/phy/meson-g12a-usb2-phy.txt

-* Amlogic G12A USB2 PHY binding
-
-Required properties:
-- compatible:	Should be "amlogic,meson-g12a-usb2-phy"
-- reg:		The base address and length of the registers
-- #phys-cells:	must be 0 (see phy-bindings.txt in this directory)
-- clocks:	a phandle to the clock of this PHY
-- clock-names:	must be "xtal"
-- resets:	a phandle to the reset line of this PHY
-- reset-names:	must be "phy"
-- phy-supply:	see phy-bindings.txt in this directory
-
-Example:
-	usb2_phy0: phy@36000 {
-		compatible = "amlogic,g12a-usb2-phy";
-		reg = <0x0 0x36000 0x0 0x2000>;
-		clocks = <&xtal>;
-		clock-names = "xtal";
-		resets = <&reset RESET_USB_PHY21>;
-		reset-names = "phy";
-		#phy-cells = <0>;
-	};