* NVIDIA Tegra Watchdog controller

Required properties:

- compatible: Should be "nvidia,tegra-wdt"
- reg: Should contain WDT and corresponding timer source
  registers location and length.

Optional properties:

- interrupts: interrupt number to the cpu
- nvidia,expiry-count: total expiry count of WDT (1 if not specified)
- nvidia,enable-on-init: Toggle switch for enable during init
- nvidia,heartbeat-init: default timeout in secs (120 secs if not specified)
- nvidia,timer-index: timer source index for WDT

Timer source index:

      There are three ways by which WDT timer source index can be specified
and timer source selection happens with below given priorty order (decending)
(a) Bootloader programs WDT and timer source
(b) "nvidia,timer-index" property in DT
(c) Timer source base address in DT (old method)

Method (a) is of highest priority, because bootloader can program the WDT timer
source and lock to prevent any further modification of timer source by kernel.
In order to calculate the timer source address in runtime in this case timer
base address is required and hence Timer base address should be provided in
timer resource property in DT.

Either timer base address or timer source address is expected in timer resource
property in DT for case (b).

Note: If method (c) is used it should correspond to the timer source index provided
in method (a) or (b) or make sure that method (a) or (b) is not in use.

Examples:

watchdog@60005100 {
	compatible = "nvidia,tegra-wdt";
	reg = <0x0 0x60005100 0x0 0x20		/* WDT0 registers */
		0x0 0x60005088 0x0 0x8>;	/* TMR0 registers */
	interrupts = <0 123 0x04>;
	nvidia,expiry-count = <4>;
	nvidia,timer-index = <7>;
	status = "disabled";
};