dt-bindings: phy: Convert Calxeda ComboPHY binding to json-schema

Convert the Calxeda ComboPHY binding to DT schema format using
json-schema.
There is no driver in the Linux kernel matching the compatible
string, but the nodes are parsed by the SATA driver, which links to them
using its port-phys property.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/phy/calxeda-combophy.txt

-Calxeda Highbank Combination Phys for SATA
-
-Properties:
-- compatible : Should be "calxeda,hb-combophy"
-- #phy-cells: Should be 1.
-- reg : Address and size for Combination Phy registers.
-- phydev: device ID for programming the combophy.
-
-Example:
-
-	combophy5: combo-phy@fff5d000 {
-		compatible = "calxeda,hb-combophy";
-		#phy-cells = <1>;
-		reg = <0xfff5d000 0x1000>;
-		phydev = <31>;
-	};
-

Documentation/devicetree/bindings/phy/calxeda-combophy.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/calxeda-combophy.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Calxeda Highbank Combination PHYs binding for SATA
+
+description: |
+  The Calxeda Combination PHYs connect the SoC to the internal fabric
+  and to SATA connectors. The PHYs support multiple protocols (SATA,
+  SGMII, PCIe) and can be assigned to different devices (SATA or XGMAC
+  controller).
+  Programming the PHYs is typically handled by those device drivers,
+  not by a dedicated PHY driver.
+
+maintainers:
+  - Andre Przywara <andre.przywara@arm.com>
+
+properties:
+  compatible:
+    const: calxeda,hb-combophy
+
+  '#phy-cells':
+    const: 1
+
+  reg:
+    maxItems: 1
+
+  phydev:
+    description: device ID for programming the ComboPHY.
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - maximum: 31
+
+required:
+  - compatible
+  - reg
+  - phydev
+  - '#phy-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    combophy5: combo-phy@fff5d000 {
+                   compatible = "calxeda,hb-combophy";
+                   #phy-cells = <1>;
+                   reg = <0xfff5d000 0x1000>;
+                   phydev = <31>;
+               };