Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix MAC address configuration for VNIC

The FDT description is as follows:
- phy-handle, reg, qlm-mode, mac-address are under nodes in bgx0/1 node
- phy nodes (pointed by phy-handle) are under MDIO even though they may
not be connected through to MDIO. In those nodes they do not contain
MAC address or etc.

This commit changes parsing of the FDT nodes for BGX so that it can
obtain correct MAC address for a given PHY.

Reviewed by: wma
Obtained from: Semihalf
Sponsored by: Cavium
Differential Revision: https://reviews.freebsd.org/D5781

Fix VNIC enumeration after r294993 and r294990

ofw_bus_get_node() must be tested against negative values since
missing parent bus method will result in calling the default method
which simply returns (-1): sys/dev/ofw/ofw_bus_if.m
This was lost in the review process.

Obtained from: Semihalf
Sponsored by: Cavium

Fix finding appropriate BGX node in DTB and move it to a separate function

Search for BGX node in DTS in two ways:
1. Try to find it uder root node first
2. If not found under root, find the top level PCI bridge node
and search all nodes below it until appropriate BGX node is found.
Move search code to another function to make the code more clear.
Remove unused variable by the way.

Reviewed by: wma
Obtained from: Semihalf
Sponsored by: Cavium
Differential Revision: https://reviews.freebsd.org/D5066

Introduce initial support for Cavium's ThunderX networking interface

- The driver consists of three main componens: PF, VF, BGX
- Requires appropriate entries in DTS and MDIO driver
- Supports only FDT configuration
- Multiple Tx queues and single Rx queue supported
- No RSS, HW checksum and TSO support
- No more than 8 queues per-IF (only one Queue Set per IF)
- HW statistics enabled
- Works in all available MAC modes (1,10,20,40G)
- Style converted to BSD according to style(9)
- The code brings lmac_if interface used by the BGX driver to
update its logical MACs state.

Obtained from: Semihalf
Sponsored by: The FreeBSD Foundation