Merge branch 'axienet-broken-link'

Andy Chiu says:

====================
Fix broken link on Xilinx's AXI Ethernet in SGMII mode

The Ethernet driver use phy-handle to reference the PCS/PMA PHY. This
could be a problem if one wants to configure an external PHY via phylink,
since it use the same phandle to get the PHY. To fix this, introduce a
dedicated pcs-handle to point to the PCS/PMA PHY and deprecate the use
of pointing it with phy-handle. A similar use case of pcs-handle can be
seen on dpaa2 as well.

--- patch v5 ---
 - Re-apply the v4 patch on the net tree.
 - Describe the pcs-handle DT binding at ethernet-controller level.
--- patch v6 ---
 - Remove "preferrably" to clearify usage of pcs_handle.
--- patch v7 ---
 - Rebase the patch on latest net/master
--- patch v8 ---
 - Rebase the patch on net-next/master
 - Add "reviewed-by" tag in PATCH 3/4: dt-bindings: net: add pcs-handle
   attribute
 - Remove "fix" tag in last commit message since this is not a critical
   bug and will not be back ported to stable.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>