I had to take eight rounds of interviews. Two were coding rounds, and the others were a mix of technical, system design, and management.

Overall, it was an exhausting process that stretched over one month. Four rounds were onsite, and the remaining were online.

Despite explicitly requesting it, I received no feedback on my performance.

I am still getting vague calls and emails.

Explain the Bluetooth (BT) implementation on Android, right from the physical/RF layer to the Android HAL (Hardware Abstraction Layer) layer. Be as elaborate as possible.