MFC r235151:

MFC r235151:
  Implement basic remote PHY support. Remote PHY allows the
  controller to perform MDIO type accesses to a remote transceiver
  using message pages defined through MRBE(multirate backplane
  ethernet).  It's used in blade systems(e.g Dell Blade m610) which
  are connected to pass-through blades rather than traditional
  switches.
  This change directly manipulates firmware's mailboxes to control
  remote PHY such that it does not use mii(4).  Alternatively, as
  David said, it could be implemented in brgphy(4) by creating a fake
  PHY and let brgphy(4) do necessary mii accesses and bce(4) can
  implement mailbox accesses based on the type of brgphy(4)'s mii
  accesses. Personally, I think it would make brgphy(4) hard to
  maintain since it would have to access many bce(4) registers in
  brgphy(4). Given that there are users who are suffering from lack
  of remote PHY support, it would be better to get working system
  rather than waiting for complete/perfect implementation.

git-svn-id: svn://svn.freebsd.org/base/stable/9@235818 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f