With this patch, "ip link add help" shows:

Usage: ip link add [ link DEV ] [ name ] NAME
                    [ txqueuelen PACKETS ]
                    [ address LLADDR ]
                    [ broadcast LLADDR ]
                    [ mtu MTU ]
                    type TYPE [ ARGS ]

        ip link set DEVICE [ { up | down } ]
                           [ arp { on | off } ]
                           [ dynamic { on | off } ]
                           [ multicast { on | off } ]
                           [ allmulticast { on | off } ]
                           [ promisc { on | off } ]
                           [ trailers { on | off } ]
                           [ txqueuelen PACKETS ]
                           [ name NEWNAME ]
                           [ address LLADDR ]
                           [ broadcast LLADDR ]
                           [ mtu MTU ]
                           [ netns PID ]
        ip link show [ DEVICE ]

TYPE := { vlan | veth | dummy | ifb | macvlan }