This is where I will post links specifically related to the mechanisms of ADHD, and what defines it.
What’s the Real Deficit in Attention Deficit/Hyperactivity Disorder?
I really liked this article - how it specified that ADHD is not a "deficiency" in attention, but rather a lack of conscious control over it. I particularly liked the section "The Neural Networks of Attention" where the author breaks down the attention process into three separate neurological responses: alerting, orienting, and executing. It makes you more aware of why the condition can be so hard to manage - because it's multi-faceted as opposed to being a singular issue.