Added a new watchdog driver which can handle a multiple wdt_dw instances
and can control the pause signal.
The mlt platform has three designware watchdogs, one for each core.
I decided to create a separate intel watchdog driver for the following
reasons:
1. All three devices share the same interrupt number. Each watchdog reports
an interrupt to the core to which it has been assigned. The same interrupt
number cannot be used by multiple devices in the device tree. So, it would
be assigned to only one device. The other dw watchdog devices would use
this assignment, even though it would not be described for them in the dt.
The interrupt handler function in dw watchdog checks the interrupt flag.
If the interrupt was connected to the first watchdog, and the second or
third watchdog signal an interrupt, the interrupt handler of the first
device would ignore it because it would not have set the interrupt flag.
The watchdog device don't knows anything about the existence of the others
devices.
2. The designware watchdog only supports a hardware pause signal. It cannot
be paused programmatically. On the mtl platform, there is a separate group
of control registers for all per-core watchdogs. There are GPIO-like
registers that allows control of a hardware pause signal for subordinate
watchdogs. This separate block is shared by all three watchdogs.
3. The base addresses of the subordinate watchdogs are read from the
aforementioned control registers. As a result, in the device tree we have
only one base address for the intel watchdog, which points to the pause
control registers and containing the base addresses of the subordinate
devices.
Signed-off-by: Adrian Warecki <adrian.warecki@intel.com>
