device-types: base-uboot: Allow adding extra boot methods

On system ready devices we usually boot from u-boot into grub. To be able to interact with such a chainloaded bootloader, a device can now use the extra_boot_methods variable.

E.g. to add grub support, you can now add the following to a device dict entry:

{% set extra_boot_methods %}
grub:
  parameters:
    bootloader_prompt: {{ bootloader_prompt|default('grub>') }}
    needs_interrupt: {{ grub_needs_interrupt|default(true) }}
grub-efi:
  parameters:
    bootloader_prompt: {{ bootloader_prompt|default('grub>') }}
    needs_interrupt: {{ grub_needs_interrupt|default(true) }}
{% endset %}

requested review from @ivoire

assigned to @ivoire

added 3 commits

• 17b9dc02...aeccedeb - 2 commits from branch master
• 11b8d8f6 - device-types: base-uboot: Allow adding extra boot methods

Compare with previous version

changed the description

mentioned in commit 80e29c68

merged

changed milestone to %2025.04