arm64: dts: allwinner: a64: Add watchdog

Add a watchdog node for the A64, automatically enabled on all boards.
Since the device is compatible with an existing driver, we only reserve
a new compatible string to be used together with the fall back.
Tested on Olimex Teres-I.
Signed-off-by: Harald Geyer <harald@ccbib.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

Documentation/devicetree/bindings/watchdog/sunxi-wdt.txt

@@ -2,8 +2,10 @@ Allwinner SoCs Watchdog timer
 
 Required properties:
 
-- compatible : should be either "allwinner,sun4i-a10-wdt" or
-               "allwinner,sun6i-a31-wdt"
+- compatible : should be one of
+	"allwinner,sun4i-a10-wdt"
+	"allwinner,sun6i-a31-wdt"
+	"allwinner,sun50i-a64-wdt","allwinner,sun6i-a31-wdt"
 - reg : Specifies base physical address and size of the registers.
 
 Example:

arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi

@@ -665,5 +665,12 @@ r_rsb: rsb@1f03400 {
 			#address-cells = <1>;
 			#size-cells = <0>;
 		};
+
+		wdt0: watchdog@1c20ca0 {
+			compatible = "allwinner,sun50i-a64-wdt",
+				     "allwinner,sun6i-a31-wdt";
+			reg = <0x01c20ca0 0x20>;
+			interrupts = <GIC_SPI 25 IRQ_TYPE_LEVEL_HIGH>;
+		};
 	};
 };