OPPO has patented a new kind of phone or phablet with an optional secondary display to which it can attach using custom-designed hinges. Therefore, this detachable portion could act as a keyboard, or perhaps allow the entire product to imitate a Surface Duo at will. The OEM has also apparently patented a mobile gaming controller with in-built earphones.
https://www.notebookcheck.net/OPPO-patents-a-new-kind-of-dual-display-mobile-device.530914.0.html