Default u-boot defconfig is
configs/imx8mq_trucrux_defconfig
Default path of Uboot
build_xwayland/tmp/work/imx8mq-trux-q01-fslc-linux/u-boot-trucrux/1.0-r0/git
To make changes in source code it is better to create a local_repos
$ cd ~/CodeSetup $ mkdir local_repos/ $ git clone https://github.com/Trucrux/uboot-trucrux.git -b v2020.04_5.4.24_2.1.0_dunfell $ cd local_repos/uboot-trucrux
Now use git to create a branch or make changes in same branch (creating new branch is recommended)
Make changes in Uboot as required.
To add changes in build
$ cd ~/CodeSetup/sources/meta-trucrux/recipies-bsp/u-boot $ touch uboot-trucrux.bbappend
(ignore if already file is created)
and append the following in bbappend file.
UBOOT_SRC = "git://${BSPDIR}/local_repos/uboot-trucrux;protocol=file" SRCBRANCH = "< branch name >" SRCREV = "< The commit id you'd like to use >"