So, how a renovate bot works is that it parses the files for a specific regular expression that we determine and checks the line after this regular expression. So it needs to be in the same json file.

For example:
{
    "sources": {
        "poky": {
            "git-remote": {
                "branch": "master",
                "describe": "4.2_M2-676-gdf3ce81ed3",
                "remotes": {
                    "origin": {
                        "uri": "https://github.com/yoctoproject/poky.git"
                    }
                },
// renovate: datasource=git-tags depName=yoctoproject/poky lookupName=https://github.com/yoctoproject/poky.git
                "rev": "df3ce81ed3e5491b084041c5bcbd16dada129cf9"
            },
            "path": "poky"
        }
    },
    "version": "1.0"
}
So, for this file, renovate bot will find the line in red beginning with "// renovate: ", and then check the next line which is "rev": "df3ce81ed3e5491b084041c5bcbd16dada129cf9", if that commit is not the latest commit, then it will replace it with the latest.