This is the only special feature on my library's DVD copy of Iron Man 3, and it's 8 and a half minutes long. It's focus is, indeed, entirely on the one sequence, one of the many stand-out ones.
Most of what we see is behind-the-scenes footage, coupled together with some clips and work-in-progress CG, pre-vis and such, and interviews explaining throughout. Yes, a lot of it was shot practically! They had actual sky-divers, at high speeds. In the air, landing in the water, holding on to each other for safety. Stark's suit itself is of course added later, they just had a stand-in, with a partial helmet. They worked with the man who allowed James Bond to leap out of a plane without a parachute as well – he knows how to hide it under clothes so that the viewer genuinely believes that they're mid-air entirely without any safety measures. They get pretty technical, but you can always follow what they're saying. Everyone had a lot of fun putting to film such a unique portion. They knew what they were doing, and it was nowhere near as dangerous as it looked, thankfully.
I recommend this to any fan of the movie. 8/10