That really isn't a correction. That is an alternative. I.e., if you happen to want to hook up to one of those cheap headsets that used to come with cellphones. I wouldn't though, since like you said, there isn't much in the way of standardization.
I was referring to the simpler case where you are wiring up just the microphone. I.e., a microphone-only jack.
There are no speakers connected to a microphone-only jack.
That helps a lot that you mention that the mic2 input already has bias applied, so it would be appropriate for a 2-wire microphone, like this: http://www.amazon.com/Xtenzi-External-Bluetooth-Microphone-Navigation
Now since I have the attention of someone who knows what he's talking about... I have THREE important questions for you that I hope you will be able to help with;
1) what would I need to do in order to achieve analog (obviously mono) line-in on mic3? (from, for example, one of these; https://www.silabs.com/Support%20Documents/TechnicalDocs/Si4736-37-38-39-C40.pdf)
2) How about mic1? There is supposedly an unpopulated point on the board to mount a first microphone, would it be possible to tap into that for a second channel line-in to make stereo?
3) i2s input. MI2S_1 aka pri_mi2s has its two data channels connected to the low speed expansion header, one of them at pin20 (PCM_DO) -- the 96boards PCM-OUT pin, and the other reassigned as GPIO-E at pin27. None of the documentation I can find suggest that either of these are restricted to audio-output, and in fact, the snapdragon 410 device specification manual on page 47 has BOTH of these identified as bi-directional. Since it is obviously more desirable to use i2s than analog where possible, (a) is it possible to use i2s-input, (b) how? And I mean software-wise (Android).