Improve samples documentation

[richbai90]

Is your feature request related to a problem? Please describe.
The samples don't include many comments explaining what each line is doing. As someone coming from a hobbyist arduino background, trying to learn the ins and outs of true embedded development, it would be extremely useful to have comments explaining what is going on.

Describe the solution you'd like
The samples make ample use of macros, which are particularly hard to follow. A simple line of explanation on a line like this const struct device *mic_dev = device_get_binding(DT_LABEL(DT_INST(0, st_mpxxdtyy))); something to the effect of get the device binding of the microphone. DT_INST is doing x, DT_LABEL is doing y, together this expands to z.

Describe alternatives you've considered
Reading the documentation. This is important, no doubt, but better code comments will help beginners.

[stephanosio]

Comments are not there to explain the obvious.

The documentation for device_get_binding, DT_LABEL and DT_INST all exist to explain what you describe here.

Of course, we could have a tutorial/special sample that has very detailed comments for the beginners, but that is a whole another issue.