concrete portal frame best practices

Maybe try the first design guide here, these guides contain a lot of useful information and are free. Not sure if it specifically covers what you are after, but usually beams from each direction have bars terminated in hooks with joint reinforcing between. Sometimes you might require vertical joint reinforcing (unlikely in an exterior joint though). Details and design might be different depending on whether you are subject/governed by seismic loading, for example joint reinforcement may need to be capacity designed for overstrength actions.

If you let everyone know what code you are working to and what your specific queries might be with this type of joint people can reply with specific information.