Merge branch 'doc-update-bridge-doc'

Hangbin Liu says:

====================
Doc: update bridge doc

The current bridge kernel doc is too old. It only pointed to the
linuxfoundation wiki page which lacks of the new features.

Here let's start the new bridge document and put all the bridge info
so new developers and users could catch up the last bridge status soon.

v3 -> v4:
- Patch01: Reference and borrow definitions from the IEEE 802.1Q-2022 standard
           for bridge (Stephen Hemminger)
- Patch04: Remind that kAPI is unstable. Add back sysfs part, but only note
           that sysfs is deprecated. (Stephen Hemminger, Florian Fainelli)
- Patch05: Mention the RSTP and IEEE 802.1D developing info. (Stephen Hemminger)
- Some other grammar fixes.

v2 -> v3:
- Split the bridge doc update and adding kAPI/uAPI field to 2 part (Nikolay Aleksandrov)
- Update bridge and bridge enum descriptions (Nikolay Aleksandrov)
- Add user space stp help for STP doc (Vladimir Oltean)

v1 -> v2:
- Update bridge and bridge port enum descriptions (Vladimir Oltean)

RFCv3 -> v1:
- Fix up various typos, grammar and technical issues (Nikolay Aleksandrov)

RFCv2 -> RFCv3:
- Update netfilter part (Florian Westphal)
- Break the one large patch in to multiparts for easy reviewing. Please tell
  me if I break it too much.. (Nikolay Aleksandrov)
- Update the description of each enum and doc (Nikolay Aleksandrov)
- Add more descriptions for STP/Multicast/VLAN.

RFCv1 -> RFCv2:
- Drop the python tool that generate iproute man page from kernel doc
====================

Link: https://lore.kernel.org/r/20231201081951.1623069-1-liuhangbin@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>