Defines a clean Hardware Abstraction Layer (HAL) for Bluetooth/Wi-Fi coexistence. The struct btc_coexist contains function pointers for I/O operations, H2C commands, and status queries. This pattern allows chip-specific implementations to be plugged in while providing a stable interface for the coexistence logic. It is isolated from the rest of the driver and could be extracted for use in other Realtek or similar combo chip drivers with minimal adaptation.

Implements a generic debugfs interface for the driver. It creates per-device directories and provides read/write handlers for dumping MAC, BB, and RF registers, as well as CAM entries. The pattern uses seq_file and user access helpers, and the code is largely self-contained (only depends on core driver structures). Could be extracted as a reusable debugfs template for any kernel driver needing register-level diagnostics.

Provides functions to read and write EFUSE (a one-time-programmable memory on Realtek chips) and emulate EEPROM shadow. The implementation handles logical-to-physical mapping, checksum validation, and write-protect. It is generic across chips (driven by parameterized struct rtl_efuse) and could be reused in other projects that need to access similar fuse-based storage in embedded devices.

A collection of preprocessor shims to enable building the driver on multiple kernel versions. It defines macros for APIs that changed over time (e.g., SIMPLE_DEV_PM_OPS, RX_FLAG_MACTIME_MPDU, IEEE80211_KEY_FLAG_SW_MGMT). This pattern is essential for out-of-tree drivers and could serve as a reference for other projects needing to bridge kernel API differences.