Bridge properties like stp do not work anymore on interface UCI types in latest 21.02

[Federico Capoano]

Hi everyone,

today I realized that some bridge and L2 properties which weren't
working anymore on OpenWrt 21.02 had to be moved from the interface
UCI type to the new device UCI type in /etc/config/network.

I thought that in this release the old syntax would continue being
supported, however I see that this is not the case, because the stp
and macaddr directives were clearly being ignored until I moved those
from "interface" to "device", I either misunderstood the previous
discussions or there's something wrong here, I also do not see much
information about this breaking change in the release notes:
https://openwrt.org/releases/21.02/notes-21.02.1, am I missing
something?

Since I maintain a system called OpenWISP which aims to ease the
configuration management of a high number of OpenWrt based devices, I
find myself in a tricky situation because OpenWISP now basically won't
work fully with OpenWrt 21.02, moreover it needs to support older
OpenWrt versions for a while, so I want to ask: do you think it's ok
to generate both type of syntaxes (old and new) at the same time?
I would assume that an old openwrt version would ignore the new syntax
while a newer openwrt version would ignore the old syntax and use the
new one.

Is there a summary of the config syntax changes?

Thanks in advance
Best regards
Federico Capoano