dt-bindings: net: dsa: add bindings for xrs700x switches

Add documentation and an example for Arrow SpeedChips XRS7000 Series
single chip Ethernet switches.
Signed-off-by: George McCollister <george.mccollister@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/arrow,xrs700x.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/dsa/arrow,xrs700x.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Arrow SpeedChips XRS7000 Series Switch Device Tree Bindings
+
+allOf:
+  - $ref: dsa.yaml#
+
+maintainers:
+  - George McCollister <george.mccollister@gmail.com>
+
+description:
+  The Arrow SpeedChips XRS7000 Series of single chip gigabit Ethernet switches
+  are designed for critical networking applications. They have up to three
+  RGMII ports and one RMII port and are managed via i2c or mdio.
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - arrow,xrs7003e
+          - arrow,xrs7003f
+          - arrow,xrs7004e
+          - arrow,xrs7004f
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        switch@8 {
+            compatible = "arrow,xrs7004e";
+            reg = <0x8>;
+
+            ethernet-ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                ethernet-port@1 {
+                    reg = <1>;
+                    label = "lan0";
+                    phy-handle = <&swphy0>;
+                    phy-mode = "rgmii-id";
+                };
+                ethernet-port@2 {
+                    reg = <2>;
+                    label = "lan1";
+                    phy-handle = <&swphy1>;
+                    phy-mode = "rgmii-id";
+                };
+                ethernet-port@3 {
+                    reg = <3>;
+                    label = "cpu";
+                    ethernet = <&fec1>;
+                    fixed-link {
+                        speed = <1000>;
+                        full-duplex;
+                    };
+                };
+            };
+        };
+    };