I've had some luck with the drm-next-4.7 on a somewhat older graphics card (Haswell), but only using 12.0-CURRENT. The last time I tried, with a snapshot from the 20th (of June), after pulling in the drm-next stuff, it wouldn't boot.
If you want to try it, I have a page I made when it worked, http://srobb.net/freebsdintel.html
It is for a different card, and as I said, it hasn't worked for me with the most recent snapshots. I _was_ able to install FreeBSD-11, then, using git, pull the drm-next stuff and that worked. However, when I did that, ports didn't work.
(I explain that briefly on the page. The few packages that I installed with pkg did work).
Did you notice, you this thread is more that 2 years old?
Broadwell Graphics have been supported since FreeBSD 11.2-RELEASE came out in June 2018.
With FreeBSD 12.0-RELEASE, drm-next-kmod got removed and was replaced by the meta port drm-kmod. It will install the proper drm port depending on your FreeBSD version.
I've been running my Broadwell equiped workstation with Iris Pro5200 graphics since June 2018, and still run it on FreeBSD 12.0-RELEASE.
I am more than happy that it works for you, but as you may notice it does not work for me on 12.0-RELEASE and this is quite a blocker, so the PR seems necessary because it is not about your "works for me" setup ;-)
This thread is about Intel HD Graphics 5500 so why should I start another one?
1. 12.0-RELEASE containt /boot/kernel/i915kms.so module that does not work with the card yet.
2. /boot/kernel/i915kms.so was shadowing the /boot/modules/i915ksm.so version from the ports, so I have to use port DRM driver and kldload /boot/modules/i915kms.so explicitly providing the full path to the module not only the kldload i915kms.so that loads the older default module from the generic kernel.
3. I have uninstalled the xf86-video-intel driver and now use modeset driver in conjuction with kernel DRM + i915kms that works better and faster.