Comment 2 for bug 1526808

In case you don't know yet: You want to start looking here:

  sudo udevadm test-builtin path_id /sys/class/net/eth0

which will say something like

D_PATH=ccwgroup-0.0.0600
ID_PATH_TAG=ccwgroup-0_0_0600

which will then result in
$ udevadm info /sys/class/net/eth0
P: /devices/qeth/0.0.0600/net/eth0
E: DEVPATH=/devices/qeth/0.0.0600/net/eth0
E: ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
E: ID_NET_NAME=enccw0.0.0600
E: ID_NET_NAME_MAC=enx02270a000012
E: ID_NET_NAME_PATH=enccw0.0.0600
E: ID_PATH=ccwgroup-0.0.0600
E: ID_PATH_TAG=ccwgroup-0_0_0600