[TF-A] [RFC] Common API to retrieve pre-allocated share memory for Transfer List

Hi,

I am currently doing research to implement the Transfer List to comply with Arm's firmware handoff spec ( https://github.com/FirmwareHandoff/firmware_handoff) in order to have a standardized handoff approach between different firmware stages during boot.

The idea is to create a Transfer List in BL2 and cache it into a pre-allocated memory in SRAM that can be shared between BL2 and BL3x.

A prototype currently available is creating APIs under qemu platform code to retrieve the pre-defined memory address (The shared memory region is defined in platform_def.h). But I think we need to define a common API for this purpose to support all platforms.

Please share your views or any suggestions.

Thanks. Regards, Raymond