Flash instructions in the OpenWRT Commit: https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=eae6cac6a30b95bef04d033ed8a303b7e35a078b

We only support v1, not v2 or v3.

At the December 2019 review day, the behavior for LAN only devices was
defined. Such devices will use each LAN port as WAN.

Hardware specification:
- SOC: Qualcomm QCA9563 @ 775MHz
- Flash: GigaDevice GD25Q64CSIG (8MiB)
- RAM: Zentel A3R1GE40JBF (128 MiB DDR2)
- Ethernet: Qualcomm QCA8337N: 4x 1Gbps LAN + 1x 1Gbps WAN
- Wireless:
  - 2.4GHz (bgn) QCA9563 integrated (3x3)
  - 5GHz (ac) Qualcomm QCA9886 (2x2)
- Button: 1x power, 1x reset, 1x wps
- LED: 6x LEDs: power, wlan2g, wlan5g, lan, wan, wps
- UART: There's no UART header on the board

many AVM devices do not have RESET/WPS buttons. So use the otherwise unused DECT/PHONE button to boot the device into setup mode.

This patch allows to enter the setup-mode by pressing the phone button
(often labeled as DECT) in addition to WPS and reset button.

This patch is necessary to allow supporting boards without a WPS and reset
button (e.g. AVM FRITZ!Box 7312).

This commit removes the broken flag for the ipq806x-generic target,
as the first device (NETGEAR R7800) now has full support in Gluon

This commit accounts for the target renaming which was done in upstream
commit 7407e723991 ("ipqx0xx: add Generic subtarget")

Their kernel partition is too small, the OpenWrt build system
is unable to create an image.

This adds a warning that entprise switches with an IGMP/MLD snooping
feature are not supported yet with IGMP/MLD filtering enabled.

For this to work, firstly the Linux bridge on the Gluon node needs to
support Multicast Router Discovery (RFC4286). But this feature was only
added to the Linux kernel recently, in 5.1.

Secondly, a Gluon node would need to periodically send "Multicast Router
Advertisment" (RFC4286) messages, to "announce" the multicast router
port setting on bridge port bat0.

Thirdly, the IGMP/MLD snooping switches would need to implement
RFC4286.

The kernel partition on these devices is too small for the
OpenWrt 19.07 kernel. It is also located after the rootfs, so
we cannot grow it further.

Therefore mark these devices as deprecated now.

Fixes #1821

This adds documentation for the gluon-mesh-batman-adv package and
elaborates on its build and configuration options, as well as
the implemented multicast architecture.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>