dt-bindings: net: add dt binding for realtek rtl82xx phy

Add binding for realtek rtl82xx phy.
Signed-off-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/realtek,rtl82xx.yaml

+# SPDX-License-Identifier: GPL-2.0+
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/realtek,rtl82xx.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek RTL82xx PHY
+
+maintainers:
+  - Andrew Lunn <andrew@lunn.ch>
+  - Florian Fainelli <f.fainelli@gmail.com>
+  - Heiner Kallweit <hkallweit1@gmail.com>
+
+description:
+  Bindings for Realtek RTL82xx PHYs
+
+allOf:
+  - $ref: ethernet-phy.yaml#
+
+properties:
+  realtek,clkout-disable:
+    type: boolean
+    description:
+      Disable CLKOUT clock, CLKOUT clock default is enabled after hardware reset.
+
+
+  realtek,aldps-enable:
+    type: boolean
+    description:
+      Enable ALDPS mode, ALDPS mode default is disabled after hardware reset.
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    mdio {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethphy1: ethernet-phy@1 {
+                reg = <1>;
+                realtek,clkout-disable;
+                realtek,aldps-enable;
+        };
+    };