rtc: Generate fdt node for the real-time clock

On arm and arm64 we expose the Motorola RTC emulation to the guest,
but never advertised this in the device tree.

EDK-2 seems to rely on this device, but on its hardcoded address. To
make this more future-proof, add a DT node with the address in it.
EDK-2 can then read the proper address from there, and we can change
this address later (with the flexible memory layout).

Please note that an arm64 Linux kernel is not ready to use this device,
there are some include files missing under arch/arm64 to compile the
driver. I hacked this up in the kernel, just to verify this DT snippet
is correct, but don't see much value in enabling this properly in

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20200514094553.135663-1-andre.przywara@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
1 file changed