The patent illustrations show the basic structure of a traditional Xbox controller that can be split into two halves. When they're in the charger, they look more like a traditional controller, much like the Joy-Cons when it's connected to the controller's device.
The modules are designed to be connected to the handheld devices so as not to overly hide the screen. The images show what appears to be two modules attached to the cheeks of a tablet, thus creating a configuration similar to that of a switch. The patent describes that controller modules can be removed when the user has finished playing, and then re-attached when they want to resume playback. The patent states that the controller could be connected to the same or another touch screen device, suggesting that the controllers are not designed for exclusive use on a single system.
The patent may possibly be linked to the Microsoft xCloud service. At E3 this year, we played Halo 5 on xCloud, using a Samsung phone connected to Xbox controllers. At the time, we had described mounting both devices as "pre-beta", and it seemed likely that a more personalized solution would eventually be used. With xCloud capable of running on phones and tablets, a controller capable of attaching itself to the sides of the device to create a configuration similar to that of a switch seems like a sensible approach.
If this is the case, then this patent could be the equivalent of the Google Stadia controller, which is also designed to be used with a multitude of devices.
Matt Purslow is the editor of IGN UK News and Entertainment. You can follow him on Twitter.