dt/bindings: Add bindings for PIC32 deadman timer peripheral

Document the devicetree bindings for the deadman timer peripheral found on
Microchip PIC32 SoC class devices.
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-watchdog@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12702/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Documentation/devicetree/bindings/watchdog/microchip,pic32-dmt.txt

+* Microchip PIC32 Deadman Timer
+
+The deadman timer is used to reset the processor in the event of a software
+malfunction. It is a free-running instruction fetch timer, which is clocked
+whenever an instruction fetch occurs until a count match occurs.
+
+Required properties:
+- compatible: must be "microchip,pic32mzda-dmt".
+- reg: physical base address of the controller and length of memory mapped
+  region.
+- clocks: phandle of parent clock (should be &PBCLK7).
+
+Example:
+
+	watchdog@1f800a00 {
+		compatible = "microchip,pic32mzda-dmt";
+		reg = <0x1f800a00 0x80>;
+		clocks = <&PBCLK7>;
+	};