What you are describing is properly known as tilt. What it means is that the optical axis of the lens is not perpendicular to the plane occupied by the camera's sensor. In your case the entire lens appears to be tilted relative to the camera's lens mounting flange.
There are specialized lenses that intentionally introduce such angles between the image plane in the camera and the optical axis of the lens. They usually include tilt movements as well as shift movements. Thus they are called Tilt/Shift or Perspective Control lenses.
Just as an aside, a decentered lens element is, in some ways, similar to a shift movement using a T/S lens. The biggest difference is that all of the elements in a T/S lens are moved together and the various pieces of glass stay in the same alignment with respect to the others. When only one lens element moves in a direction perpendicular to the optical axis of the lens it results in degraded image quality because it is no longer aligned with the other elements in the lens.
You could also get the same result if the camera/lens system is perfectly self aligned but the entire system is improperly aligned with the test chart. The sensor and test chart must be parallel to one another or one side of the chart (or the top, or the bottom) will be closer to the camera than the other. This will result in only one part of the chart being in focus at any particular focus distance.
For a good explanation of the difference between decentered, tilted, and mis-spaced lens elements (with illustrations) and how to test for each, please see Roger Cicala's excellent blog entry titled: Testing for a Decentered Lens: an Old Technique Gets a Makeover