allowed.
- ``port_vlan_add``: bridge layer function invoked when a VLAN is configured
- (tagged or untagged) for the given switch port..
+ (tagged or untagged) for the given switch port. The CPU port becomes a member
+ of a VLAN only if a foreign bridge port is also a member of it (and
+ forwarding needs to take place in software), or the VLAN is installed to the
+ VLAN group of the bridge device itself, for termination purposes
+ (``bridge vlan add dev br0 vid 100 self``). VLANs on shared ports are
+ reference counted and removed when there is no user left. Drivers do not need
+ to manually install a VLAN on the CPU port.
- ``port_vlan_del``: bridge layer function invoked when a VLAN is removed from the
given switch port