First let me thank you for your work :)
Using 5.12 rc two and three I encounter consistent hangs on shutdown with the dmesg/journal showing call traces. On shutdown the machine stays in half awake state instead of reaching poweroff. On suspend it behaves similar but recovers desktop usage after about 20s. Wireless adapter doesn't return until pci rescan.
Running fine using 5.11 except for Intel graphics thus my expedition into mainland and I did not test on 5.12rc1.
Machine manages to poweroff when I unload brcmfmac before shutdown.
Machine: x86_64 intel atom x7-8350
Adapter: BCM4356
Kernel: Linux 5.12.0-rc3-1-mainline Arch
wpa_supplicant 2:2.9-8
NetworkManager 1.30.2-1