Thank you for your tips. I was doing everything correctly (maybe). Because I found compiled lan78xx.ko. Previously I was looking in the wrong folder. And my second mistake was that after flashing image into Omega I expected that module will be list when I type lsmod but it lists only installed modules but not the statically built-in kernel. Does someone know how to list kernel built-in modules? Tip for somebody who needs a driver that source is part of the kernel already. make kernel_menuconfig find there your driver and mark it * for the static part of the kernel or M for a module. make world or only recompile kernel - it is much faster. make target/linux/compile you will find compiled .ko if you want to install it with insmod or you can continue with make target/linux/install and make target/install and you will get new .bin image with recompiled kernel