I'm using Yocto to build an embedded environment. I want to change the actual recipe of generation of bootloader. Exist a graphical tool to edit the u-boot recipe? Or how can I change the packages available in u-boot image?
What kind of board are you using? From the NXP forum, I have found a document on modifying the U-boot for Freescale i.MX6X. It contains information about U-boot Set Up, Image Install Instruction, How to use U-boot, etc. The link is here
To find the u-boot and modify, you need to look at the machine configuration. In there, it will shows where the kernel and u-boot comes from.
For example, the iMX6 sabrelite
Then, find the bsp for u-boot recipe for the compatible machine In there, at URI, you will find the git repository that tell where the u-boot is, change the branch and clone the u-boot.
Then, do whatever you want to modify the u-boot. After that, point your machine u-boot URI to where you store the u-boot repository.