Not sure if his actual discharge was recorded or was burned during the civil war. But here are some sources if you haven't checked them out yet. There is a pretty good narrative on the following link.
Dear Mr. Nighan,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the series Indexes to the Carded Records of Soldiers Who Served in Volunteer Organizations During the Civil War, 1899 - 1927 in the Records of the Adjutant General's Office, 1762 - 1917 (Record Group 94) that includes an index card for [New York] DeYo, Ira N - Unit: 85th Infantry, Company: B - Enlistment Rank: Pvt, Discharge Rank: Cor.
The index card indicates that there should be a Compiled Military Service Record (CMSR) form him in Carded Records Showing Military Service of Soldiers Who Fought in Volunteer Organizations During the American Civil War in the Records of the Adjutant General's Office, 1762 - 1917 (Record Group 94). Most of the service records in this series have been made available via microfilm and through digitization of the microfilm. Unfortunately, the bulk of the records for New York Volunteers have not been microfilmed or digitized. There also may be a pension file for him, however if there is, it has also not been digitized. These records are in the custody of the National Archives at Washington, DC - Textual Reference (RDT1), which can be contacted at Archives1reference@nara.gov.
In regards to your specific request for discharge papers, while the CMSR typically lists the discharge date, the War Department did not retain a copy of the discharge certificates given to soldiers. Pension files sometimes contain discharge certificates submitted in support of claims, although even in pension files this is the exception rather than the norm. For more information about what types of information is typically included in these records, see Civil War Records: Basic Research Sources.
To order records that have not already been digitized, please fill out a NATF Form 86 for the service records and a NATF Form 85 for the pension records and mail the completed forms to the address listed on the form. You also may place your order online using eservices.archives.gov. For more information see Requesting Copies of Older (pre-WWI) Military Service Records.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT1. Also, the National Archives and Records Administration (NARA) has suspended reproduction and digitization services until further notice due to COVID-19. Orders will not be serviced until operations can resume safely. Once operations resume, document reproduction requests will be filled in the order in which they were received. We apologize for any inconvenience.
The New York State Archives may have additional records concerning New York soldiers and units.
We hope this information is helpful. Best of luck with your family research!