ubuntu@localhost:~$ cat /etc/udev/rules.d/80-snappy_oem-hardware-assign_oem-hardware-assign_serial-monitor.rules 
KERNEL=="ttyS0", TAG:="snappy-assign", ENV{SNAPPY_APP}:="oem-hardware-assign_serial-monitor"

KERNEL=="ttyUSB0", TAG:="snappy-assign", ENV{SNAPPY_APP}:="oem-hardware-assign_serial-monitor"

ubuntu@localhost:~$ sudo udevadm info -n /dev/ttyS0 -q all
P: /devices/pnp0/00:05/tty/ttyS0
N: ttyS0
E: DEVNAME=/dev/ttyS0
E: DEVPATH=/devices/pnp0/00:05/tty/ttyS0
E: MAJOR=4
E: MINOR=64
E: SUBSYSTEM=tty
E: TAGS=:systemd:
E: USEC_INITIALIZED=50692