Enhancements to the YANG Language for Capturing Subtree Replacements

As YANG data models evolve over time, model nodes are often deprecated or made obsolete. Current practices for documenting replacement paths for these nodes rely on unstructured external documents, making it difficult to programmatically identify and migrate to replacement nodes. This document proposes a YANG extension mechanism that embeds replacement path information directly within YANG models, enabling automation tools to identify replacement nodes and assist users in migrating from deprecated elements to their replacements.