Add a simple FDT based mailbox framework which is built on top of the generic
mailbox library. The phandle of FDT mailbox DT node is treated as the unique
mailbox controller ID which is required by the generic mailbox library. The
FDT based mailbox drivers will be probed on-demand from fdt_mailbox_request_chan()
called by the mailbox client drivers.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Add generic mailbox library which is independent of hardware description
format. The OpenSBI platform support or mailbox drivers can register
mailbox controller instances which can be discovered and used by different
mailbox client drivers. Each mailbox controller instance has a unique ID
which can be used by mailbox client drivers for find the mailbox controller
instance. The mailbox client drivers will typically request a mailbox channel
from the mailbox controller and use it to do data transfer with the remote
end of mailbox channel.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
