dt-bindings: serial: describe SA8255p

dt-bindings: serial: describe SA8255p

SA8255p platform abstracts resources such as clocks, interconnect and
GPIO pins configuration in Firmware. SCMI power and perf protocols are
used to send request for resource configurations.

Add DT bindings for the QUP GENI UART controller on sa8255p platform.

The wakeup interrupt (IRQ) is treated as optional, as not all UART
instances have a wakeup-capable interrupt routed via the PDC.

Signed-off-by: Nikunj Kela <quic_nkela@quicinc.com>
Co-developed-by: Praveen Talari <quic_ptalari@quicinc.com>
Signed-off-by: Praveen Talari <quic_ptalari@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250721174532.14022-2-quic_ptalari@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>