dt-bindings: net: dsa: Add documentation for Hellcreek switches

Add basic documentation and example.
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/hirschmann,hellcreek.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/dsa/hirschmann,hellcreek.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Hirschmann Hellcreek TSN Switch Device Tree Bindings
+
+allOf:
+  - $ref: dsa.yaml#
+
+maintainers:
+  - Andrew Lunn <andrew@lunn.ch>
+  - Florian Fainelli <f.fainelli@gmail.com>
+  - Vivien Didelot <vivien.didelot@gmail.com>
+  - Kurt Kanzenbach <kurt@linutronix.de>
+
+description:
+  The Hellcreek TSN Switch IP is a 802.1Q Ethernet compliant switch. It supports
+  the Precision Time Protocol, Hardware Timestamping as well the Time Aware
+  Shaper.
+
+properties:
+  compatible:
+    items:
+      - const: hirschmann,hellcreek-de1soc-r1
+
+  reg:
+    description:
+      The physical base address and size of TSN and PTP memory base
+    minItems: 2
+    maxItems: 2
+
+  reg-names:
+    items:
+      - const: tsn
+      - const: ptp
+
+  leds:
+    type: object
+    properties:
+      '#address-cells':
+        const: 1
+      '#size-cells':
+        const: 0
+
+    patternProperties:
+      "^led@[01]$":
+        type: object
+        description: Hellcreek leds
+        $ref: ../../leds/common.yaml#
+
+        properties:
+          reg:
+            items:
+              - enum: [0, 1]
+            description: Led number
+
+          label: true
+
+          default-state: true
+
+        required:
+          - reg
+
+        additionalProperties: false
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - ethernet-ports
+  - leds
+
+unevaluatedProperties: false
+
+examples:
+  - |
+        switch0: switch@ff240000 {
+            compatible = "hirschmann,hellcreek-de1soc-r1";
+            reg = <0xff240000 0x1000>,
+                  <0xff250000 0x1000>;
+            reg-names = "tsn", "ptp";
+            dsa,member = <0 0>;
+
+            ethernet-ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+                    label = "cpu";
+                    ethernet = <&gmac0>;
+                };
+
+                port@2 {
+                    reg = <2>;
+                    label = "lan0";
+                    phy-handle = <&phy1>;
+                };
+
+                port@3 {
+                    reg = <3>;
+                    label = "lan1";
+                    phy-handle = <&phy2>;
+                };
+            };
+
+            leds {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                led@0 {
+                    reg = <0>;
+                    label = "sync_good";
+                    default-state = "on";
+                };
+
+                led@1 {
+                    reg = <1>;
+                    label = "is_gm";
+                    default-state = "off";
+                };
+            };
+        };