dt-bindings: mips: Add EcoNet platform binding

Document the top-level device tree binding for EcoNet MIPS-based SoCs.

Signed-off-by: Caleb James DeLisle <cjd@cjdns.fr>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: cjdelisle

Documentation/devicetree/bindings/mips/econet.yaml

@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mips/econet.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: EcoNet MIPS SoCs
+
+maintainers:
+  - Caleb James DeLisle <cjd@cjdns.fr>
+
+properties:
+  $nodename:
+    const: '/'
+
+  compatible:
+    oneOf:
+      - description: Boards with EcoNet EN751221 family SoC
+        items:
+          - enum:
+              - smartfiber,xp8421-b
+          - const: econet,en751221
+
+additionalProperties: true
+
+...