[M] Change in coreboot[master]: UNTESTED acpi: Add ECAM region below PNP0C02 device in SSDT

[Arthur Heymans (Code Review)]

Attention is currently required from: Angel Pons, Jeff Daly, Lance Zhao, Matt DeVillier, Nico Huber, Sean Rhodes, Tim Wawrzynczak, Vanessa Eusebio.

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/75729?usp=email )

Change subject: UNTESTED acpi: Add ECAM region below PNP0C02 device in SSDT
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Patch Set 3:

(1 comment)

File src/acpi/acpi.c:

https://review.coreboot.org/c/coreboot/+/75729/comment/166a9d5f_40144b6c :
PS2, Line 587: 	struct device *dev = dev_find_path(NULL, DEVICE_PATH_DOMAIN);
             : 	assert(dev != NULL);
> Anyway, a different thought: This is probably not the right place to decide
> what device we add the resource to. Technically we already have the
> `.acpi_fill_ssdt` pointer for this. We could set it to a default implementation
> depending on CONFIG_ECAM_MMCONF_SUPPORT. And if a platform has its own
> fill_ssdt(), it could still call the default one. WDYT?

I agree, but I'd prefer not hook that up to each platform in .acpi_fill_ssdt.
Would adding a dummy device at runtime using a bootstate hook that has this in .acpi_fill_ssdt be an acceptable solution to avoid hooking it up everywhere? Maybe with a Kconfig so that it can still be overriden if desired?