netdev_master_upper_dev_link — Add a master link to the upper device
| int netdev_master_upper_dev_link ( | struct net_device * dev, | 
| struct net_device * upper_dev ); | 
Adds a link to device which is upper to this one. In this case, only one master upper device can be linked, although other non-master devices might be linked as well. The caller must hold the RTNL lock. On a failure a negative errno code is returned. On success the reference counts are adjusted and the function returns zero.