It is correct that you should not have to provide this extreme degree of accommodation. I am just making a supposition here, but based on my own lifetime experience having pretty serious and disruptive ADHD, I know that one of the primary ways this condition expresses itself in people with ADHD is what is called "Time Blindness". No, this is NOT a "get out of jail free" card. It is simply an incredibly well-researched by neuroscientists precept that communicates not only is this a serious problem zone for the person, but also in many way it is out of her or his control. To a point!
I am simply saying it is highly possible this student suffers from all sorts of processing lag cognitive problems, and task management executive functionsd such that it could be a serious struggle for them. As easy as it is for outsiders to be dismissive of, or disbelieving in, the level of control such an ADHD person has in relation to managing this real problem, it is in fact a very well-known facet of the disorder. (See neuroscience and ADHD expert Dr. Russell Barkley on this topic on his youtube channel, and/or expert sites from CHADD, ADDA, ADDitude Magazine, verywellmind).
NOTE: This answer will likely be too detailed and need editing, but I am writing it because I believe it is important.
Since ADHD is a recognized disability under the law, it is at minimal useful for people in yours and other professions to have some minimal knowledge of this. And it is very common that in educational/learning environments, such students are often provided some forms of accommodation to help the student.
My purpose in writing this however is to state that this kind of persistent or constant lateness, coupled with the student's expectation that you help "catch him or her up" is way out of scope for "reasonable accommodation". In this possible scenario I am presenting, the student would likely be aware that she or he has been diagnosed with ADHD, thus knowing or learning about this common executive function struggle. In which case an initial presentation of these problems showing up might lead to a student requesting some form of catch-up help. IF this were an initial problem showing up, and a teacher were to be informed of this, along with a request "could you please help me catch up?", I would consider that a reasonable request. But as many many have stated, any kind of ongoing expectation of "catch up sessions because I was late" is completely out of bounds, and, again as many have stated, completely unsustainable for you with your workload and responsibilities. The corrected expectation, to me, would be "You've got to figure out a way to mitigate these lateness struggles. It will require work and effort by you, whether it means setting multiple alarms to ensure you wake up not just ON TIME but with additional padded time to account for unforeseen circumstances (be they transportation hiccups, or behavioral breakdowns, whatever).
The flip side to the many uncontrollable, or hard to control, signal processing functions inherent to ADHD is that research also shows that ADHD people tend to have incredibly adaptive & creative mechanisms to problem solve for both the chronic lateness problem as well as the "how do I catch up on the material I missed due to lateness".
I like the answers and suggestions re having a "catch-up mechanism in place." In the end, I am (1) providing a possible context for the chronic lateness, while (2) also stating adamantly that the solution to this student's problem is not incumbent solely on you. My scenario here may not even be remotely at play with this student; could be something else entirely. Still, I would recommend at least having the conversation once with this student to ascertain "Do you know if ADHD is possibly behind this problem?" and if it is, empathy is a remarkable force multiplier in helping to talk over what he or she might be able to do to better regulate and accommodate their own problem. But beyond placing the issue on the table, and perhaps initially (early on!) accommodating the request for some catch up session, it should be made perfectly clear that as much as you may sympathize, it is the student's responsibility to mitigate this chronic problem.
Lastly I want to state that, again, as incredulous as it may seem to some people, you would be surprised just how many people exhibit the wide array of symptoms of the neurological disorder, yet have zero awareness that they possibly even have the disorder. One salient illustration. I got mostly straight-A's from grade school, high school, on through college. Yet because of my age and era of growing up, nobody in the 1960's and 70's were ever screened for ADHD because it was largely unknown except in the most esoteric of situations. Did I know I had problems with being late, with losing things all the time, forgetting things mid-sentence, having stressful breakdowns because too many noises, voices or other distractions would knock my thoughts and attention straight out of my head? Yeah, I knew it very well. But even with 45 years of different therapists & doctors, nobody ever, not in the 80's, not in the 90's, not in the 2000's, ever once pointed out "Has anyone ever told you you might have ADHD?". Only at age 63 did an ER doctor ever pose the question -- turns out yes I had it diagnosed, and no matter when it was diagnosed, you had the condition your entire life.