The entire section "Kept you waiting, huh?" is about this and some of the background is really interesting explaining why things are as they are. Here's just the last bit:

> Luckily for us, Sven was up to the task of dealing with all this nonsense. It just took slightly longer than expected! While the patchset to enable Thunderbolt was sent upstream first (another massive win for us!), we have also pulled it into our downstream kernel and are now shipping it to users!

> But there is a catch. Currently, only USB3, XDomain and Thunderbolt Networking are supported. You can plug in USB devices or connect two Thunderbolt computers together and make them ping each other, but that’s about it. PCIe and DisplayPort tunnelling — required for most Thunderbolt docks — are not supported. Yet. Watch this space.

> An enormous amount of gratitude is owed to Sven, who has stuck with this thankless chore for nearly 5 years in between all of his other incredible work.

Thank you, Sven!