I'm not sure I'm understanding the question here. If you just want to render your image to open in photoshop, just choose whatever you want the final image rendered as in Maya's Render Globals (along with the alpha channel box ticked if necessary)...using tiff or targa is fine. Then, simply open up the file in photoshop. If you have the plugin that allows photoshop to read .iff, that'll work also. Then just do you editing in photoshop and save as jpg or whatever you want depending on your needs..

Take a look at some of our free videos on Render Globals, Intro to Compositing, or Setting up Image Planes for Reference. They may help you out.