Merge branch 'phy-doc-improvements'

Merge branch 'phy-doc-improvements'

Florian Fainelli says:

====================
Documentation: net: phy: Improve documentation

This patch series addresses discussions and feedback that was recently received
on the mailing-list in the area of: flow control/pause frames, interpretation of
phy_interface_t and finally add some links to useful standards documents.

Changes in v3:

- add Timur's feedback into patch 3

Changes in v2:

- clarify a few things in the RGMII section, add a paragraph about common issues
  with RGMII delay mismatches
====================

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