how to order by and group by equal column values in SQL? [duplicate]

My table is:

device_name | device_category
---------------------------------
standard_spot | light
mobile_spot | light
tracker | light
smoking_machine| light
microphone1 | sound
microphone2 | sound
display1_hmdi | projector
display1_vga | projector
display1_sound | projector


I need a query that provides the device_names together with the device_categories ordered by the occurrence of a device_category. My attempt was this query, which provides the occurrences of each category:

SELECT COUNT(*) AS num_dcats FROM `devices` GROUP BY device_category ORDER BY num_dcats DESC


Like this:

device_category | num_dcats
---------------------------
light | 4
projector | 3
sound | 2

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