It's a pretty standard driver model internal abstraction layer.
In kernel space you as the hardware manufacturer implement a display miniport driver, and heavily lean on dxgkrnl.sys
https://learn.microsoft.com/en-us/windows-hardware/drivers/d...
And implement interfaces like this one for D3D12 https://learn.microsoft.com/en-us/windows-hardware/drivers/d...
There's quite a bit though and it's kind of spread across several sections on MSDN.