dt-bindings: watchdog: xlnx,versal-wwdt: Add versal watchdog

Versal watchdog IP uses window watchdog mode. Window watchdog
timer(WWDT) contains closed(first) and open(second) window with
32 bit width. Write to the watchdog timer within predefined window
periods of time. This means a period that is not too soon and
a period that is not too late.

Add devicetree bindings for versal window watchdog device.

Signed-off-by: Srinivas Neeli <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/xlnx,versal-wwdt.yaml

···
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/xlnx,versal-wwdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Xilinx Versal window watchdog timer controller
+
+maintainers:
+  - Neeli Srinivas <[e-mail]>
+
+description:
+  Versal watchdog intellectual property uses window watchdog mode.
+  Window watchdog timer(WWDT) contains closed(first) and open(second)
+  window with 32 bit width. Write to the watchdog timer within
+  predefined window periods of time. This means a period that is not
+  too soon and a period that is not too late. The WWDT has to be
+  restarted within the open window time. If software tries to restart
+  WWDT outside of the open window time period, it generates a reset.
+
+allOf:
+  - $ref: watchdog.yaml#
+
+properties:
+  compatible:
+    enum:
+      - xlnx,versal-wwdt
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    watchdog@fd4d0000 {
+        compatible = "xlnx,versal-wwdt";
+        reg = <0xfd4d0000 0x10000>;
+        clocks = <&clock25>;
+        timeout-sec = <30>;
+    };
+...