Change in coreboot[master]: soc/mediatek: Add PCIe support

[Shelley Chen (Code Review)]

Attention is currently required from: Hung-Te Lin, Furquan Shaikh, Yu-Ping Wu, Jianjun Wang.
Shelley Chen has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/56791 )

Change subject: soc/mediatek: Add PCIe support
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Patch Set 6:

(1 comment)

File src/soc/mediatek/common/pcie.c:

https://review.coreboot.org/c/coreboot/+/56791/comment/4c23d633_9239fd4e 
PS2, Line 329: mtk_pcie_gen3_probe
> Furquan is no longer in the team. […]

Hi Jianjun, thanks for putting this together.

As Furquan mentioned above, there is a pci_domain_ops callback structure that you can use to pull in the platform-specific functions:

static struct device_operations pci_domain_ops = {
    .read_resources   = &pci_domain_read_resources,
    .set_resources    = &pci_domain_set_resources,
    .scan_bus         = &pci_domain_scan_bus,
};

the pci_domain_* functions are generic and already defined.  If you need to add anything platform-specific, you can define your own functions and replace the associated field as appropriate.

You can define the pci_domain_ops callback struct in the soc.c file for your soc (src/soc/mediatek/mt8195/soc.c ).