https://blog.csdn.net/Luckiers/article/details/123586094

read

https://blog.csdn.net/lijunjun1120/article/details/108804438
https://blog.csdn.net/weixin_29798865/article/details/116812987

write

https://blog.csdn.net/qq_22847457/article/details/91622840
ty_write的函数又调用n_tty_write函数来实现，n_tty_write又调用uart_write函数(位于drivers/tty/serial/serial_core.c)