Migration starts with the project you already have. RouteRTL reads a vendor project and writes a declarative project description; it does not require you to rewrite the RTL first.
Import
For a Vivado project:
rr migrate run path/to/project.xpr
The migration step discovers source files, the top-level design, and the target information it can read from the project. Review the generated files before running a build.
Compare
Keep the original project available while you compare outputs:
rr migrate verify \ --original-project path/to/project.xpr
Verification is a comparison step, not a claim that every vendor-specific feature has been translated. Constraints, generated IP, and block-design details still need review where the original project depends on them.
Result
The useful result is a project that can be inspected as YAML and then passed
through the same rr commands as a new project. If migration reports a gap,
keep the original project as the reference and file the unsupported construct;
do not hide it in a hand-written vendor script.