I am experimenting with creating a .deb package and am unsure about the file structure of a package. Is the directory that contains control, changelog, rules, etc supposed to be named DEBIAN or debian?

I am using dpkg-deb to package it, and it seems to require DEBIAN, and I am trying to use Lintian to check it, and it isn't recognizing the changelog or copyright files. Lintian throws the errors debian-changelog-file-missing and no-copyright-file but later warns unknown-control-file changelog and unknown-control-file copyright. Looking at this page, it suggests using debian, and I rename the directory to that but it causes dpkg-deb to fail. Reading through the Debian Policy Manual, it usually uses debian in examples, but occasionally uses DEBIAN, which makes me wonder if in certain circumstances both may be needed. What is the right way to do this?