One such claim is https://gamevice.com/. It is suing Nintendo over an alleged infringement of patent over the design of the controller. Gamevice claims it is the owner of the patent for a free-hand and detachable controller.
The above links to the filed patent and was filed in 2015 in respect of a “Combination Computing Device and Game Controller with Flexible Bridge Section”. Should Nintendo be worried? Probably not! Nintendo sold just under 5 million units so far so a deal if the patent has legs will probably be done.
The pitfalls of success!