Дополнительный UART в U-Boot
If you do not want to switch these variables,
because you still want output on the default UART
you will have to access the device driver.
Unfortunately drivers/serial/serial-uclass.c
does not yet export functions for this.
But _serial_putc(), __serial_getc(), and __serial_tstc()
should give you an idea how this is done.
Lovely Llama