The product guide for the Video Processing Subsystem (PG231 from November 18, 2015) is not clear on some of the color mappings.
Particularly, Tables 2-5, 2-6, and 2-7.
Regarding Table 2-5 (Dual Pixels per Clock, 10 Bits per Component Mappint for YUV 4:2:2), 4:2:2 has 2 channels.
One channel carries Y and the second channel carries U and V interleaved in time, starting with U every line.
So when you do this for 2 pixels per clock, the mapping is as follows:
4:2:0 adds vertical subsampling to 4:2:2 which is implemented in the AXI4 Stream by simply omitting the Chroma data on every other line.
For example, for the first line in the frame (i.e. line 0 which is even) is mapped:
Now, because the odd lines do not contain a valid Chroma component, they look like this: