We'll want to eventually match (for VLAN) a given hardware address
that's not the device's hardware address.  Only the device itself
knows which NMSetting should contain it's hardware address (ie
the 'wired' setting for NMDeviceEthernet, 'infiniband' for
NMDeviceInfiniband, etc) and VLANs take their hardware address
from the parent interface.  So eventually we'll have VLAN
interfaces use these new arguments to ask their parent interface
to match the VLAN hardware address in a connection, since the
VLAN doesn't know (or need to know) what kind of interface it
really is underneath.