dt-bindings: watchdog: Add YAML schemas for the generic watchdog bindings

The watchdogs have a bunch of generic properties that are needed in a
device tree. Add a YAML schemas for those.

Signed-off-by: Maxime Ripard <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/watchdog.yaml

···
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/watchdog.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Watchdog Generic Bindings
+
+maintainers:
+  - Guenter Roeck <[e-mail]>
+  - Wim Van Sebroeck <[e-mail]>
+
+description: |
+  This document describes generic bindings which can be used to
+  describe watchdog devices in a device tree.
+
+properties:
+  $nodename:
+    pattern: "^watchdog(@.*|-[0-9a-f])?$"
+
+  timeout-sec:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Contains the watchdog timeout in seconds.
+
+...