Most of the larger cruise ships cater very well for disabled passengers and have dedicated disabled cabins available. The facilities these offer can vary quite a lot from ship to ship but generally the larger and newer the ship the better the facilities.
It is very important that you advise the cruise line of the level of disability and any specific requirements. Things such as hoists should be asked about before booking, but I believe these can be either arranged by the cruise line or arrangements made for you to bring your own onboard. These companies have dedicated staff to ensure everything possible is done to help you and that embarking and disembarking is as easy as possible. However it may not be possible for them to disembark you at every port, especially if they have to use tender boats to get passengers ashore.
I have had personal experience of travelling with wheelchair users on both P&O Cruises and Cunard, and both had a very good understanding of the extra needs of the disabled.
I hope this helps .