Internal, adds an interface to a bridge

def _bsd_addif(br, iface):
    '''
    Internal, adds an interface to a bridge
    '''
    kernel = __grains__['kernel']
    if kernel == 'NetBSD':
        cmd = _tool_path('brconfig')
        brcmd = 'add'
    else:
        cmd = _tool_path('ifconfig')
        brcmd = 'addem'

    if not br or not iface:
        return False

    return __salt__['cmd.run']('{0} {1} {2} {3}'.format(cmd, br, brcmd, iface),
                               python_shell=False)