PDCA, in more humanities than engineering terms, is basically the final Agile Principle “At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.”

https://agilemanifesto.org/principles.html

This is PDCA:

> Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage.

And the sibling has the one that states PDCA for the development process too.