A/D converter on ClearFog

Device tree file armada-388-clearfog.dtsi lists a Microchip MCP3021 A/D converter on the base board, and it appears to actually be there, maybe U16. I haven’t yet located any description of this. What analog signal is sitting at the input? Or is it pinned out someplace convenient where I could feed it a signal?
Note that in the device tree source it is named as “mikrobus_adc”, although it is actually under I2C bus 0, not bus 1.

Yes it is under bus 0. I believe this got changed in later revs of the board and the mainline device-tree doesn’t properly reflect it. The A/D converter is connected to the AN pin of the mikrobus header for use by mikrobus based expansion boards.