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Buildroot has ample documentation.  Be careful that the version of the documentation matches the version your buildroot.  The documentation that you should read comes with the download of buildroot at docs/manual/manual.text.

Submitting your changes

You must submit whatever SLAC-specific changes you've made back to the git repo.  Create a branch the indicates which version of buildroot your changes are to be applied on top of.  The convention for the branch name is:

• br-<year>.<month>-<version>

I will use br-2019.08-2 since my changes represent the second SLAC release of the 2019.08 version of buildroot.