/PATH=(n1[.n2.n3.n4.n5.n6])

    Specifies the path to the device on the bus. The path is used
    to uniquely identify a device if the device does not have a
    serial number. The path specification is a series of six or fewer
    numbers,

    where:

    n1               is the number of the root hub (at tier 0).

    n2 through n6    are port numbers for downstream hubs at tiers 1,
                     2, 3, 4, and 5.

    For example, /PATH=1.4.3 indicates that the device is in turn
    plugged into port 3 of the second tier, which is plugged into
    port 4 of the first tier, which in turn is plugged into the root
    hub 1.