if peripheral clock is not configured, uart init API function returns 0, so we need to check the return value of this function Signed-off-by: Andrei-Edward Popa <andrei_edward.popa@upb.ro>
Added a serial driver for the RP2040. Only polling API is supported. Signed-off-by: Yonatan Schachter <yonatan.schachter@gmail.com>