dt-bindings: net: Add tsnep Ethernet controller

The TSN endpoint Ethernet MAC is a FPGA based network device for
real-time communication.

It is integrated as normal Ethernet controller with
ethernet-controller.yaml and mdio.yaml.
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/engleder,tsnep.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/engleder,tsnep.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TSN endpoint Ethernet MAC binding
+
+maintainers:
+  - Gerhard Engleder <gerhard@engleder-embedded.com>
+
+allOf:
+  - $ref: ethernet-controller.yaml#
+
+properties:
+  compatible:
+    const: engleder,tsnep
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  local-mac-address: true
+
+  mac-address: true
+
+  nvmem-cells: true
+
+  nvmem-cells-names: true
+
+  phy-connection-type:
+    enum:
+      - mii
+      - gmii
+      - rgmii
+      - rgmii-id
+
+  phy-mode: true
+
+  phy-handle: true
+
+  mdio:
+    type: object
+    $ref: "mdio.yaml#"
+    description: optional node for embedded MDIO controller
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    axi {
+        #address-cells = <2>;
+        #size-cells = <2>;
+        tnsep0: ethernet@a0000000 {
+            compatible = "engleder,tsnep";
+            reg = <0x0 0xa0000000 0x0 0x10000>;
+            interrupts = <0 89 1>;
+            interrupt-parent = <&gic>;
+            local-mac-address = [00 00 00 00 00 00];
+            phy-mode = "rgmii";
+            phy-handle = <&phy0>;
+            mdio {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                suppress-preamble;
+                phy0: ethernet-phy@1 {
+                    reg = <1>;
+                    rxc-skew-ps = <1080>;
+                };
+            };
+        };
+    };