Merge tag 'doc-2026-04-rc2' of https://source.denx.de/u-boot/custodians/u-boot-efi

Pull request doc-2026-04-rc2

Documentation:

* describe QEMU VGA emulation
* development process
  - Move the existing block about patch application
  - Rework the custodian feedback section
  - Explain when/how Custodians may edit patches
  - Move Custodians section
  - Make "Work flow of a Custodian" a subsection
  - Document using b4 and patchwork for custodians
* develop: codingstyle: Update b4 external link
* develop: sending_patches: Update link to patchwork