def intf_id_from_uni_port_num(port_num):
    """
    Extract the PON device port number from a virtual UNI Port number

    :param port_num: (int) virtual UNI / vENET port number on OLT PON
    :return: (int) PON Port number (note, this is not the PON ID)
    """
    return (port_num >> 11) & 0xF