How to create /dev/tty0

Create tty0~tty15

CONFIG_VT=y

Create ttyS0

CONFIG_SERIAL_CONSOLE=y

enable ttyS0 with systemctl (test on Debian Jessie)

# systemctl enable serial-getty@ttyS0.service
It will create the link file in /etc/systemd/system/getty.target.wants
ex: 
# ls /etc/systemd/system/getty.target.wants
  serial-getty@ttyS0.service -> /lib/systemd/system/serial-getty@.service


# systemctl mask serial-getty@ttyS0.service
It will link to /dev/null in /etc/systemd/system/
ex: 
# ls /etc/systemd/system/serial-getty@ttyS0.service -> /dev/null


# systemctl disable serial-getty@ttyS0.service
It will remove the file in /etc/systemd/system/getty.target.wants

ref:
1. Here
2. stackoverflow
3. Pid Eins