What qualifies a community as a master planned? What documents need to be filed?

A Master Planned Community is sometimes referred to as a city, or a subdivision within a city. These developments usually have multiple neighborhoods and one or multiple builders within each neighborhood. These communities are usually created by community planning builders that buys and clears unmanned land and they build multiple similar or homes with different elevations and plat the property a certain way. The areas usually have a deed restriction set in place that they homeowners must abide by to keep the neighborhood in order, and protect the neighborhood's value and appearance. Some have neighborhood amenities (such as parks, recreational centers, tennis courts, basketball courts, playgrounds, and/or clubhouses) and/or an HOA or POA to keep up the appearance of the neighborhood and manage access & maintenance of the community's amenities. Some also have schools within the neighborhood as well.
There are really no documents to file when you are creating a master planned community. See the article link below. I hope that this information helps.

https://www.useful-community-development.org/community-planning-process.html

A Master Planned Community is one where there are far more amenities than average such as hiking/biking trails, lakes, golf courses etc. MPC's have everthing within for the residents often that includes pools, gyms, tennis courts.

Bankrate.com
https://www.bankrate.com/glossary/m/master-planned-community/