docs: Document driver API conventions in README.

Author: nedseb

README.md

@@ -459,12 +459,19 @@ lib/<component>/
 
 ### Coding conventions
 
-- **Constants**: use `from micropython import const` in `const.py` files.
+- **Constants**: use `from micropython import const` wrapper in `const.py` files.
 - **Naming**: `snake_case` for new methods. Legacy `camelCase` is acceptable for I2C helpers to stay consistent with existing drivers.
 - **Class inheritance**: `class Foo(object):` is the existing convention.
-- **Time**: use `from time import sleep_ms` (not `utime`).
+- **Time**: use `from time import sleep_ms` (not `utime`, not `sleep()` with float seconds).
+- **Exceptions**: use `except Exception:` instead of bare `except:`.
 - **No debug `print()`** in production driver code.
 
+### Driver API conventions
+
+- **Constructor signature**: `def __init__(self, i2c, ..., address=DEFAULT_ADDR)` — first parameter is always `i2c` (not `bus`), address uses keyword argument with a default from `const.py`.
+- **Attributes**: `self.i2c` for the I2C bus, `self.address` for the device address (not `self.bus`, `self.addr`).
+- **I2C helpers**: use private snake_case methods `_read_reg()`, `_write_reg()` for register access. Legacy names (`setReg`, `getReg`, `i2cReadBytes`, etc.) are acceptable in existing drivers but new drivers must use the standard naming.
+
 ### Linting
 
 The project uses [ruff](https://docs.astral.sh/ruff/) (config in `pyproject.toml`).