An 1894 marriage is probably a little too 'recent' for inclusion in the online parish records, most of the NLI films only cover up to the 1880s, so the only option may be to order a research cert costing 4 euro from the GRO. See option 1 at this link
Are you certain there's a cross-matrch for this Lynch Doyle marriage on the index ?
I see a marriage entry for a Patrick Lynch marriage in Dublin South in the 3rd quarter of 1894 with references volume 2, page 619, but dont see a Mary Doyle entry with matching details... There is a Mary Doyle marriage listed int he same quarter and district, but with a different page number 588. The possible brides, i.e. with index entries matching the entry for Patrick, appear to be Rosanna Fay, Mary Anne Donnelly, Mary Anne Ennis, Mary Anne Carroll, and based on the enhanced GRO index it appears that Patrick married Rosanna Fay on the 1st July 1894
p.s. have you found your Mary & Patrick on the 1901 and 1911 census ?