iio: document "serialnumber" sysfs attribute

Add ABI documentation for the new "serialnumber" sysfs attribute. The
first user is the bno055 IIO driver.

Signed-off-by: Andrea Merello <andrea.merello@iit.it>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220907132205.28021-11-andrea.merello@iit.it
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index c79b3fd..6ba34c0 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -2155,3 +2155,10 @@ Contact: linux-iio@vger.kernel.org
 Description:
                Raw (unscaled) euler angles readings. Units after
                application of scale are deg.
+
+What:          /sys/bus/iio/devices/iio:deviceX/serialnumber
+KernelVersion: 6.1
+Contact:       linux-iio@vger.kernel.org
+Description:
+               An example format is 16-bytes, 2-digits-per-byte, HEX-string
+               representing the sensor unique ID number.