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 <maxime.ripard@bootlin.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190821143835.7294-1-mripard@kernel.orgSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

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 <linux@roeck-us.net>
+  - Wim Van Sebroeck <wim@linux-watchdog.org>
+
+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.
+
+...