Hello
I asked on linux-arm-kernel mail list regarding the "missing" dtb file problem for odroid hc2. The info i got was that the hc1 dtb file is the correct one to use for hc2 too and there is a patch to make uboot detect and use the right dtb file.
The patch in question: http://git.denx.de/?p=u-boot.git;a=patch;h=9cd97c5b049a9a282dda0b1782cbb38d8...
I rebuilt uboot-tools-2018.09-1.fc29.x86_64 with this patch applied and it boots and uses the hc1 dtb file correctly. No need for a manual symlink like: ln -s exynos5422-odroidhc1.dtb exynos5422-odroidunknown.dtb
So would be nice if this could be considered for inclusion in the fedora uboot package sometime in the future to make it easier to get the hc2 up and running.