Merging approach : how do we merge defect fixes and enhancements made across the platform implementations into the main branch?

@angshuonline , @n0man , Could you please help me understand the approach on how we merge defect fixes / enhancements across several implementations or made by the community, into the main platform? And, is this the general approach followed by developer community of DPGs/Open source platforms? Please share any relevant conversation threads, documentation, etc on the same. Thanks a ton!

@maheshwari.neha03 This page may help.