civic9

Ok, it was quite simple. Working sample s905_autoscript (static configuration, dhcp should also work):
setenv m "1080p50hz" setenv hpd "false" setenv mbpp "32" setenv bootargs "root=LABEL=rootfs rootwait ro console=ttyS0,115200n8 console=tty0 no_console_suspend hdmimode=${m} m_bpp=${mbpp} net.ifnames= 0 fsck.repair=yes elevator=noop disablehpd=${hpd} consoleblank=0 hdmitx=cecf" setenv boot_start booti 0x11000000 0x13000000 0x1000000 setenv ethaddr C0:12:34:56:78:90 setenv ipaddr 192.168.1.231 setenv serverip 192.168.1.248 tftp 0x13000000 uInitrd tftp 0x11000000 Image tftp 0x1000000 dtb.img run boot_start Now I can change kernel/initrd/dtb images without moving sd card to another device
I will probably change root to NFS too. 
It should be faster ans safer  than sd cards..