It varies from dog to dog - most will eat once per day but some will eath two or even tree times per day. It is more important to ensure that the overall daily quantity is correct and that the food is fresh - if your dog is eating more than once a day then ensure that the food is fresh when it is served - particularly in warm weather.
It depends on the age of the dog young puppies under 6 months should get 3-4 small meals per day totaling about 1-1/2 cups depending on the pups wieght. This is to prevent a hypoglocimia attck. Small dogs blood suger can drop quickly but this isn't a major problem once the dogs immune system is built up (about 4-6 month). It is reccommended that adult dogs eat twice a day so not over indulge at one meal! For a more accurate idea talk to a veteranrian for your dogs nutritional needs; small dogs need higher protien levels and higher calcium levels. your vet can recommend a quality food and amount. I believe a full gron yorkie should not have more then 3 cups dry food per day!