I managed to write H3 HDMI driver for mainline U-Boot. Source can be found here:
You should also add CONFIG_VIDEO=y to defconfig for your board.
It should work nicely for standard resolutions (720p, 1080p). Other resolutions might work, but some additional work needs to be done. Currently, this can be used for working with U-Boot (instead of serial console) or splash screen.
thank jernej share this ;
discuss on armbian forum:
https://forum.armbian.com/index.php/topic/2864-h2h3h5a64-disp2-u-boot-video-driver/