Apple filed a patent on the 28th of January, 2020 (it’s unclear if this is the actual filing date) which showcases scenarios in which an iPhone or an iPad can be docked onto a MacBook. The patent is numbered 10,545,542 at USPTO
“The appearance of a portable computing device, including its design and its heft, is important to a user, as the outward appearance contributes to the overall impression that the user has of the portable computing device,” the patent reads. “However, due to restrictive amount of available space, the portable computing device can require additional resources to provide extended functionality.”
One of the image (or drawing) shows an iPhone being docked onto the area where the trackpad of the MacBook lies. Another image shows an iPad being docked on the screen area of the MacBook to basically add keyboard functionality to the iPad. The images show the iPhone and the iPad with home button, so these images may be old and the functionality may never actually come to practical use.
“[The] electronic accessory device can be considered a ‘thin’ device, in that it extends the functionality of another device but is inoperable by itself as a stand-alone device. As such, the accessory device can have little or no independent processing resources in the form of a CPU or similar comprehensive processor.”
“The accessory device, however, can provide auxiliary processing resources, such a graphical processing unit, or GPU, or other processing resources that can support the functions of the portable computing device”.
“[It] is anticipated that the accessory device is not a stand-alone computing device but only acts in concert with a host device. The host device can be a portable computing device, such as, for example, a smart phone, media player, tablet computer, or other portable computing device”.