Like the Apple TV, there is an interesting set of unused solder pads near the edge of the logic board. These are likely used for testing during development.

The Qualcomm PM8028 chip works in conjunction with the Qualcomm MDM6600 to provide wireless data connection to the phone.

Dialog D1815A power management IC is in the Apple branded package labeled 338S0876.

Avago A2FIO46

Skyworks SKY77711 and SKY77710 power amplifiers

These photos belie how small all these chips are. We'd be lost without the help of a good camera lens and a magnifying loupe.