I skipped the following files because they were not simple.
I'll create separate PRs.
arch/xtensa/src/esp32/esp32_cpustart.c
arch/xtensa/src/common/xtensa_abi.h
boards/xtensa/esp32/esp32-core/include/board.h
Also, I skipped the following files and directories because
they looked too huge and/or foreign.
arch/xtensa/include/esp32/tie.h
arch/xtensa/include/xtensa/xtensa_corebits.h
arch/xtensa/src/esp32/hardware/
arch/xtensa/include/esp32/tie-asm.h
arch/xtensa/include/esp32/core-isa.h
arch/xtensa/include/xtensa/core.h
I also fixed a few "is is" style typos when unwrapping long lines.
* Simplify EINTR/ECANCEL error handling
1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx
* Unify the void cast usage
1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro