Most experts recommend that you not share an ADHD diagnosis with your employer. While there are laws in the US to protect individuals with disabilities (ADA), it’s very easy for employers to create other reasons for poor job performance. Plus, it’s human nature that they’ll treat you differently and be hyperaware of looking for problems.
Here are a couple articles on your rights in the workplace:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism