device - List of raw network device names attached to this zone, e.g. ppp+ to match any PPP interface.
What I find confusing:
- device vs. interface in the same sentence and appearing sort of conflicting
- how can ppp+ be considered a raw device at all, e.g. considering  stipulating
pppoe-$interfaceas interface but there is no
I would have thought that a raw netdev is a physical port, such as ethX or lanX, probably also radioX.
Thus appreciate to learn what counts as raw netdev and what defines it in the OpenWrt context/lingo.