welcome to IMSLP and thankyou for your contribution. Are you actually the composer Fazıl Say? If so, we merely require some acknowledgement that permission is granted for your Jazz Fantasy to be posted here. If you are not him, then you will need to contact him to obtain permission in writing for the score to remain here.
Also bear in mind that legally, we cannot mark this as in the public domain – absurdly, under some countries' laws, living composers cannot declare their works as public domain – however, we can mark a work as non-public domain & permission granted, with copyright falling under one of the Creative Commons licences. There are a range of possible licences which are fairly close to the spirit of "public domain".