Display notch support

[Caleb Connolly]

With many more non-desktop form factor devices landing in the kernel, 
we're starting to run up against some limitations. Notably devices with 
display notches, cutouts and rounded corners.

Given that the DRI subsystem already deals with physical display 
properties like panel orientation which is fixed in device tree, it 
would make sense to also define other properties like parts of the 
display which are obscured there too. This can then be read by desktop 
environments and UI elements can be suitably adjusted.

Android already deals with non-square displays, however they also keep 
the device configuration in userspace: 
https://developer.android.com/guide/topics/display-cutout

A solution to make this configuration generic and exposed by the kernel 
would standardise this across Linux and potentially Android too which 
would be extremely beneficial to the mobile Linux community at large.

Does this seem like a feasible solution to solving the notch problem and 
avoiding a situation where every compositor have their own method of 
describing cutouts and rounded corners?

Regards,

Caleb