Related post on forum: https://forum.turris.cz/t/combination-of-syslog-ng-luci-system-logging-configuration-mwan3/5975
Code with logread: https://gitlab.labs.nic.cz/turris/turris-os-packages/blob/test/net/mwan3-luci/files/usr/lib/lua/luci/controller/mwan3.lua#L116