For my graduation assignment I'm going to design a completely new UI for my company's software. One of the requirements my university imposes is that the entire process be based on a project management methodology. Which one is doesn't matter, as long as there's some proper structure behind it. I've googled around a bit but every one I can find (like SCRUM, Prince2, UCD) feature for a large part the actual development of the UI, which in my case is unnecessary.
So, are there any methodologies out there that focus solely on the design of interfaces? (Ideally Garrett's Planes of UX shape into project management)