1DOs and DON'Ts for designing and writing Devicetree bindings
2
3This is a list of common review feedback items focused on binding design. With
4every rule, there are exceptions and bindings have many gray areas.
5
6For guidelines related to patches, see
7Documentation/devicetree/bindings/submitting-patches.txt
8
9
10Overall design
11
12- DO attempt to make bindings complete even if a driver doesn't support some
13  features. For example, if a device has an interrupt, then include the
14  'interrupts' property even if the driver is only polled mode.
15
16- DON'T refer to Linux or "device driver" in bindings. Bindings should be
17  based on what the hardware has, not what an OS and driver currently support.
18
19- DO use node names matching the class of the device. Many standard names are
20  defined in the DT Spec. If there isn't one, consider adding it.
21
22- DO check that the example matches the documentation especially after making
23  review changes.
24
25- DON'T create nodes just for the sake of instantiating drivers. Multi-function
26  devices only need child nodes when the child nodes have their own DT
27  resources. A single node can be multiple providers (e.g. clocks and resets).
28
29- DON'T use 'syscon' alone without a specific compatible string. A 'syscon'
30  hardware block should have a compatible string unique enough to infer the
31  register layout of the entire block (at a minimum).
32
33
34Properties
35
36- DO make 'compatible' properties specific. DON'T use wildcards in compatible
37  strings. DO use fallback compatibles when devices are the same as or a subset
38  of prior implementations. DO add new compatibles in case there are new
39  features or bugs.
40
41- DO use a vendor prefix on device specific property names. Consider if
42  properties could be common among devices of the same class. Check other
43  existing bindings for similar devices.
44
45- DON'T redefine common properties. Just reference the definition and define
46  constraints specific to the device.
47
48- DO use common property unit suffixes for properties with scientific units.
49  See property-units.txt.
50
51- DO define properties in terms of constraints. How many entries? What are
52  possible values? What is the order?
53
54
55Board/SoC .dts Files
56
57- DO put all MMIO devices under a bus node and not at the top-level.
58
59- DO use non-empty 'ranges' to limit the size of child buses/devices. 64-bit
60  platforms don't need all devices to have 64-bit address and size.
61