arch/[risc-v|xtensa]/src/common: Create SoC-specific initialization routine

[tmedicci]

Summary

• arch/[risc-v|xtensa]/src/common: Create SoC-specific initialization routine

Adds a function that can be implemented by any vendor to allow SoC-specific functions to be called by up_initialize. Please note that up_initialize is provided by the arch level, but it doesn't allow SoC-specific initialization. Although it could be possible to run such initialization on board-level, semantically
it isn't related to the board, but with the SoC. As an example of such implementation, some SoCs require RTC subsystem initialization to occur before the OS is completely initialized.

Impact

Impact on user: No.

Impact on build: No.

Impact on hardware: Yes. It allows performing SoC-specific initialization that is not board-dependent.

Impact on documentation: No.

Impact on security: No.

Impact on compatibility: No.

Testing

There is no specific testing for it at this moment. There is no implementation of it yet. This PR is part of a bigger refactor on Espressif devices to simplify its boot-up process and remove code from board-level, making it easier to support new SoCs.

For this moment, ostest on affected architectures may ensure that there is no compatibility issue. Taking ESP32-C6 as an example:

Building

make -j distclean && ./tools/configure.sh -S esp32c6-devkitc:ostest && make flash ESPTOOL_PORT=/dev/ttyUSB0 ESPTOOL_BINDIR=./ -s -j$(nproc) && picocom -b 115200 /dev/ttyUSB0

Running

Run ostest as usual.

Results

nsh> ostest
.
.
.
ostest_main: Exiting with status 0