Link to the Bus Device docs.

conf.py

@@ -319,4 +319,6 @@ texinfo_documents = [
 
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'http://docs.python.org/': None}
+intersphinx_mapping = {'http://docs.python.org/': None,
+                       'https://circuitpython.readthedocs.io/projects/bus_device/en/latest/': None,
+                       'https://circuitpython.readthedocs.io/projects/register/en/latest/': None}

docs/drivers.rst

@@ -7,6 +7,7 @@ with CircuitPython and may or may not work with `MicroPython <https://micropytho
 .. toctree::
 
     Register Library <https://circuitpython.readthedocs.io/projects/register/en/latest/>
+    BusDevice Library <https://circuitpython.readthedocs.io/projects/bus_device/en/latest/>
     RGB Displays <http://micropython-rgb.readthedocs.io/>
     Analog-to-digital converters: ADS1015 and ADS1115 <http://micropython-ads1015.readthedocs.io/>
     DS3231 Real-time Clock (Precision RTC) <https://circuitpython.readthedocs.io/projects/ds3231/en/latest/>

shared-bindings/nativeio/I2C.c

@@ -42,6 +42,14 @@
 //|   physical level it consists of 2 wires: SCL and SDA, the clock and data
 //|   lines respectively.
 //|
+//|   .. seealso:: Using this class directly requires careful lock management.
+//|       Instead, use :class:`~adafruit_bus_device.i2c_device.I2CDevice` to
+//|       manage locks.
+//|
+//|   .. seealso:: Using this class to directly read registers requires manual
+//|       bit unpacking. Instead, use an existing driver or make one with
+//|       :ref:`Register <register-module-reference>` data descriptors.
+//|
 //|   :param ~microcontroller.Pin scl: The clock pin
 //|   :param ~microcontroller.Pin sda: The data pin
 //|   :param int frequency: The clock frequency

shared-bindings/nativeio/SPI.c

@@ -52,6 +52,14 @@
 //|
 //|    Construct an SPI object on the given pins.
 //|
+//|   .. seealso:: Using this class directly requires careful lock management.
+//|       Instead, use :class:`~adafruit_bus_device.spi_device.SPIDevice` to
+//|       manage locks.
+//|
+//|   .. seealso:: Using this class to directly read registers requires manual
+//|       bit unpacking. Instead, use an existing driver or make one with
+//|       :ref:`Register <register-module-reference>` data descriptors.
+//|
 //|   :param ~microcontroller.Pin clock: the pin to use for the clock.
 //|   :param ~microcontroller.Pin MOSI: the Master Out Slave In pin.
 //|   :param ~microcontroller.Pin MISO: the Master In Slave Out pin.