when I booting into system then open a terminal to run below command will work,
systemctl enable serial-getty@ttymxc0.service
but system booting still failed, check boot status
systemctl status serial-getty@ttymxc0.service
will show Active: inactive(dead)
Dependency failed for Serial Getty on ttymxc0
Job serial-getty@ttymxc0.service start failed with result 'dependency'