| The NEC-NFPA 70 does not address fire or smoke alarm issues, however is addressed by the National Fire Protection Association document NFPA 72 National Fire Alarm Code.
NFPA 72 only REQUIRES a detector on each level of a dwelling and one outside every "sleeping area", but recommneds that one be located INSIDE each bedroom.
All of the NFPA codes are adopted by all 50 US states and all US territories, and are allowed to be modified, and the recommedation to have one detector INSIDE each bedroom is widely adopted as mandatory code by the AHJ, or Authority Having Jurisdiction, which can be the local or state Fire Marshall, local Fire Chief or Deputy, etc.
So, either exceed the code and install one detector on each level, or floor, and one in each bedroom, or check with the local AHJ to learn what the specific code in your area requires.
No code would require just a detector in the "master bedroom", that clearly does not make sense. | 
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