The default BSP provided by NXP requires login in UART after booting up, which seems “unfriendly” to some users.
In i.MX Yocto BSP, Login is provided by a systemd service called systemd-serialgetty:
This service will execute agetty when system booting up and require login.
So there are two ways to disable login:
ExecStart=/bin/login -f root
Add option -a to provide username to agetty.