docs: iio: ad7380: add support for single-ended parts

The AD7380 family has some compatible single-ended chips: AD7386/7/8(-4).
These single-ended chips have a  2:1 multiplexer in front of each ADC.
They also include additional configuration registers that allow for either
manual selection or automatic switching (sequencer mode), of the
multiplexer inputs. Add a section to describe this.
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240731-ad7380-add-single-ended-chips-v2-7-cd63bf05744c@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/iio/ad7380.rst

@@ -17,10 +17,16 @@ The following chips are supported by this driver:
 * `AD7381 <https://www.analog.com/en/products/ad7381.html>`_
 * `AD7383 <https://www.analog.com/en/products/ad7383.html>`_
 * `AD7384 <https://www.analog.com/en/products/ad7384.html>`_
+* `AD7386 <https://www.analog.com/en/products/ad7386.html>`_
+* `AD7387 <https://www.analog.com/en/products/ad7387.html>`_
+* `AD7388 <https://www.analog.com/en/products/ad7388.html>`_
 * `AD7380-4 <https://www.analog.com/en/products/ad7380-4.html>`_
 * `AD7381-4 <https://www.analog.com/en/products/ad7381-4.html>`_
 * `AD7383-4 <https://www.analog.com/en/products/ad7383-4.html>`_
 * `AD7384-4 <https://www.analog.com/en/products/ad7384-4.html>`_
+* `AD7386-4 <https://www.analog.com/en/products/ad7386-4.html>`_
+* `AD7387-4 <https://www.analog.com/en/products/ad7387-4.html>`_
+* `AD7388-4 <https://www.analog.com/en/products/ad7388-4.html>`_
 
 
 Supported features
@@ -69,6 +75,42 @@ must restart iiod using the following command:
 
 	root:~# systemctl restart iiod
 
+Channel selection and sequencer (single-end chips only)
+-------------------------------------------------------
+
+Single-ended chips of this family (ad7386/7/8(-4)) have a 2:1 multiplexer in
+front of each ADC. They also include additional configuration registers that
+allow for either manual selection or automatic switching (sequencer mode), of
+the multiplexer inputs.
+
+From an IIO point of view, all inputs are exported, i.e ad7386/7/8
+export 4 channels and ad7386-4/7-4/8-4 export 8 channels.
+
+Inputs ``AinX0`` of multiplexers correspond to the first half of IIO channels (i.e
+0-1 or 0-3) and inputs ``AinX1`` correspond to second half (i.e 2-3 or 4-7).
+Example for AD7386/7/8 (2 channels parts):
+
+.. code-block::
+
+	   IIO   | AD7386/7/8
+	         |         +----------------------------
+	         |         |     _____        ______
+	         |         |    |     |      |      |
+	voltage0 | AinA0 --|--->|     |      |      |
+	         |         |    | mux |----->| ADCA |---
+	voltage2 | AinA1 --|--->|     |      |      |
+	         |         |    |_____|      |_____ |
+	         |         |     _____        ______
+	         |         |    |     |      |      |
+	voltage1 | AinB0 --|--->|     |      |      |
+	         |         |    | mux |----->| ADCB |---
+	voltage3 | AinB1 --|--->|     |      |      |
+	         |         |    |_____|      |______|
+	         |         |
+	         |         +----------------------------
+
+
+When enabling sequencer mode, the effective sampling rate is divided by two.
 
 Unimplemented features
 ----------------------