Dealing with custom hardware on x86

[Chris Packham]

Hi,

I'm about to start a project involving custom hardware using an x86 CPU. 
Complicating things somewhat we will have a CPU board supplied by a 3rd 
party vendor using a COM Express type 7 connector which will plug in to 
the board we're designing (actually 2 different boards each with some 
modular aspects) .

Coming from an embedded (mostly ARM) background I'm used to describing 
the hardware via a devicetree and dealing with plug-in modules by 
loading devicetree overlays. How do people achieve this kind of thing on 
x86?

I gather ACPI is involved somewhere but the knowledge that the BIOS has 
will go as far as the COM Express header and somehow we'll have to tell 
the kernel about the various non-probeable (mostly i2c) devices on our 
board which is kind of where I'm stuck. Any pointers would be greatly 
appreciated.

Thanks,
Chris