I've found this topic from @Maximilian-Gerhardt (Thank you for your excellent guide), explaining how to build kernel module for Omega2. I've found this in his topic:
It conveniently compiled the hello-world.ko file and even created an ipk package.
Unfortunetly, trying to installing that package will give you a kernel mismatch error
because the kernel hashes differ (see this link). Loading the .ko file directly will still work though.
So, I'm able to compile the kernel modules I need (copying the .ko files in /lib/modules/4.4.74/, but the ipk still does not match.
Any suggestions to compile ipk kernel modules for official firmware?