Update:
Now i am trying to completely disable console output.

I edited target/linux/ar71xx/image/Makefile and set CONSOLE=null, it works, no output at ttyATH0, but dbus-daemon doesn't start from init script now. I can start it manually, but it does not work automatically. No idea why. And i need dbus-daemon for my project.

I tried to add loglevel=0 into CMDLINE of target/linux/ar71xx/image/Makefile, it works too, but i still get some output from procd and kernel after startup.

I tried to set conloglevel and kconloglevel in /etc/config/system - does not work at all
kernel.printk=0 4 1 7 in /etc/sysctl.conf does not work either

Any ideas how can i disable console output + keep dbus-daemon running?

ps. /etc/inittab is without ::askconsole:/bin/ash --login too