[coreboot] Question about the devicetree.cb

[Maxim Gusev]

Hi friends!
I really hope for your help in understanding this challenge.

My questions will be about the devicetree.cb file in mainboards directories.

There are chips devices and registers in the tree.
As I understood a chip may be made up of one or more devices.
Also, some chips (for example southbridge) require configuration prior to the device configuration.
There are different device types also.

As it written in the https://www.coreboot.org/Creating_A_devicetree.cb
"A device needs to be listed in the mainboard devicetree.cb if it requires more setup than standard PCI initialization (resource allocation) \
A device needs to be listed in the mainboard devicetree.cb if it requires more setup than standard PCI initialization (resource allocation). \
Typically, that includes the CPU, northbridge, southbridge, and Super I/O. \
These devices are usually required for system specific configuration as well as indicate the system bus structure (pci_domain)".

As I understood during the coreboot PCI scan process some function (what is it name?) traverses this device tree and calls customized initialization via the device_operations and the chip_operations structures.
So the question is... Can I don't specify some PCI devices on the mainboard in the device tree if they don't need additional initialization
except to the allocation of resources?
And why do I need to specify the device tree structure.
Is there a function that traverses it and finds some device (without numeration) to initialize it? In this search that function needs the tree.
Is the device tree passed then to the kernel of the operating system (modified)?
As I can see the i2c is listed in the tree also (I am using the asus f2a85-m mainboard as an example). Does the searching of the SPD data is produced during the traversal of this tree? This question refers the other initialization (except PCI).

Thank you very much for your advice.
If you have any documentation or records on this matter - please share them.
Sorry for any stupid questions until I can understand it. I am the beginner to this.

Regards
Maxim
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