drivers serial native ptty: Split in top and bottom

Split the native ptty serial driver in a top and bottom
to enable using it with embedded libCs.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

boards/posix/native_sim/doc/index.rst

@@ -120,7 +120,7 @@ host libC (:kconfig:option:`CONFIG_EXTERNAL_LIBC`).
  input, input SDL touch, :kconfig:option:`CONFIG_INPUT_SDL_TOUCH`, host libC
  log backend, native backend, :kconfig:option:`CONFIG_LOG_BACKEND_NATIVE_POSIX`, all
  rtc, RTC emul, :kconfig:option:`CONFIG_RTC_EMUL`, all
- serial, uart native posix/PTTY, :kconfig:option:`CONFIG_UART_NATIVE_POSIX`, host libC
+ serial, uart native posix/PTTY, :kconfig:option:`CONFIG_UART_NATIVE_POSIX`, all
  serial, uart native TTY, :kconfig:option:`CONFIG_UART_NATIVE_TTY`, host libC
  spi, SPI emul, :kconfig:option:`CONFIG_SPI_EMUL`, all
  system tick, native_posix timer, :kconfig:option:`CONFIG_NATIVE_POSIX_TIMER`, all

drivers/serial/CMakeLists.txt

@@ -68,7 +68,12 @@ zephyr_library_sources_ifdef(CONFIG_USERSPACE uart_handlers.c)
 
 if(CONFIG_UART_NATIVE_POSIX)
  zephyr_library_compile_definitions(NO_POSIX_CHEATS)
- zephyr_library_sources(uart_native_posix.c)
+ zephyr_library_sources(uart_native_ptty.c)
+ if (CONFIG_NATIVE_APPLICATION)
+ zephyr_library_sources(uart_native_ptty_bottom.c)
+ else()
+ target_sources(native_simulator INTERFACE uart_native_ptty_bottom.c)
+ endif()
 endif()
 
 if(CONFIG_UART_NATIVE_TTY)

drivers/serial/Kconfig.native_posix

@@ -4,7 +4,6 @@ config UART_NATIVE_POSIX
  bool "UART driver for native_posix"
  default y
  depends on DT_HAS_ZEPHYR_NATIVE_POSIX_UART_ENABLED
- depends on EXTERNAL_LIBC
  select SERIAL_HAS_DRIVER
  help
  This enables a UART driver for the POSIX ARCH with up to 2 UARTs.