Decks are often built before patios are installed to allow frost footings to be placed without disrupting the concrete slab.  It is best not to attempt building both projects at the same time to allow you to focus your attention on the job at hand. If you are planning on installing a concrete patio below the position of your stair landing you will need to adjust your stair design to properly land on it once it is completed.  You may need to postpone your final deck inspection until the patio is installed for the stairs to meet the uniform riser and tread requirements.  In the meantime you should brace the bottoms of the stairs.