Answer
There is three ways to set the regualtory domain from release version 8.5.0.7 on.
1. as a command line parameter when loading the brcmfmac.ko module. Example:
# insmod brcmfmac.ko regdomain="US"
2. in a config file in your root fs:
# cat /etc/modprobe.d/brcmfmac.conf
options brcmfmac regdomain=US
3. Device Tree setting
Device Tree setting is preferred. See Lairds Software Integration Guiide (SIG) on Github:
Sterling LWBx Series Radio Software Integration Guide
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