dt-bindings: watchdog: Add ARM smc wdt for mt8173 watchdog

This watchdog can be used on ARM systems with a Secure
Monitor firmware to forward watchdog operations to
firmware via a Secure Monitor Call.
Signed-off-by: Evan Benn <evanbenn@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20200505131242.v6.1.Id96574f1f52479d7a2f3b866b8a0552ab8c03d7f@changeidSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/arm-smc-wdt.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/arm-smc-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM Secure Monitor Call based watchdog
+
+allOf:
+  - $ref: "watchdog.yaml#"
+
+maintainers:
+  - Julius Werner <jwerner@chromium.org>
+
+properties:
+  compatible:
+    enum:
+      - arm,smc-wdt
+  arm,smc-id:
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      The ATF smc function id used by the firmware.
+      Defaults to 0x82003D06 if unset.
+
+required:
+  - compatible
+
+examples:
+  - |
+    watchdog {
+      compatible = "arm,smc-wdt";
+      arm,smc-id = <0x82003D06>;
+      timeout-sec = <15>;
+    };
+
+...

MAINTAINERS

@@ -1456,6 +1456,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/interrupt-controller/arm,vic.txt
 F:	drivers/irqchip/irq-vic.c
 
+ARM SMC WATCHDOG DRIVER
+M:	Julius Werner <jwerner@chromium.org>
+R:	Evan Benn <evanbenn@chromium.org>
+S:	Maintained
+F:	devicetree/bindings/watchdog/arm-smc-wdt.yaml
+
 ARM SMMU DRIVERS
 M:	Will Deacon <will@kernel.org>
 R:	Robin Murphy <robin.murphy@arm.com>