FDT overlays support for ubdlr

[gonzo]

Summary

Add support for DTB overlays to ubldr:

• Add handler for fdt_overlays variable to ubldr.

"fdt_overlays" is coma-separated list of overlay files. ubldr would try to load files one by one from /boot/dtb/ and right before final DTB fixup it would try to apply them to current FDT blob. Variable can be either u-boot env variable or loader env variable.

[imp]

Are these changes from upstream dtc?

[gonzo]

In D3180#63461, @imp wrote:

Are these changes from upstream dtc?

Not from official tree as far as I understand. I merged this patch:
https://github.com/RobertCNelson/dtc/commit/dd6a0533e846e8d5e690a618fa35cc15a6103efb

[imp]

In D3180#63462, @gonzo wrote:

In D3180#63461, @imp wrote:

Are these changes from upstream dtc?

Not from official tree as far as I understand. I merged this patch:
https://github.com/RobertCNelson/dtc/commit/dd6a0533e846e8d5e690a618fa35cc15a6103efb

We need to be careful integrating it. We don't want to create a permanent fork...

This is really cool and needful stuff, though, so I'm torn.

[manu_bidouilliste.com]

Even if the overlay isn't standard it would be nice to commit the ubldr support.
And maybe provide a ports/pkg for the non-standard dtc ?

[gonzo]

Remove dtc patch as non-standard, leave only ubldr part. It still can be used with vendor-provided .dtb/.dtbo files