1.. SPDX-License-Identifier: GPL-2.0 2 3========================================== 4Submitting Devicetree (DT) binding patches 5========================================== 6 7I. For patch submitters 8======================= 9 10 0) Normal patch submission rules from 11 Documentation/process/submitting-patches.rst applies. 12 13 1) The Documentation/ and include/dt-bindings/ portion of the patch should 14 be a separate patch. The preferred subject prefix for binding patches is:: 15 16 "dt-bindings: <binding dir>: ..." 17 18 Few subsystems, like ASoC, media, regulators and SPI, expect reverse order 19 of the prefixes:: 20 21 "<binding dir>: dt-bindings: ..." 22 23 The 80 characters of the subject are precious. It is recommended to not 24 use "Documentation" or "doc" because that is implied. All bindings are 25 docs. Repeating "binding" again should also be avoided. 26 27 2) DT binding files are written in DT schema format using json-schema 28 vocabulary and YAML file format. The DT binding files must pass validation 29 by running:: 30 31 make dt_binding_check 32 33 See Documentation/devicetree/bindings/writing-schema.rst for more details 34 about schema and tools setup. 35 36 3) DT binding files should be dual licensed. The preferred license tag is 37 (GPL-2.0-only OR BSD-2-Clause). 38 39 4) Submit the entire series to the devicetree mailinglist at 40 41 devicetree@vger.kernel.org 42 43 and Cc: the DT maintainers. Use scripts/get_maintainer.pl to identify 44 all of the DT maintainers. 45 46 5) The Documentation/ portion of the patch should come in the series before 47 the code implementing the binding. 48 49 6) Any compatible strings used in a chip or board DTS file must be 50 previously documented in the corresponding DT binding file 51 in Documentation/devicetree/bindings. This rule applies even if 52 the Linux device driver does not yet match on the compatible 53 string. [ checkpatch will emit warnings if this step is not 54 followed as of commit bff5da4335256513497cc8c79f9a9d1665e09864 55 ("checkpatch: add DT compatible string documentation checks"). ] 56 57 7) DTS is treated in general as driver-independent hardware description, thus 58 any DTS patches, regardless whether using existing or new bindings, should 59 be placed at the end of patchset to indicate no dependency of drivers on 60 the DTS. DTS will be anyway applied through separate tree or branch, so 61 different order would indicate the serie is non-bisectable. 62 63 If a driver subsystem maintainer prefers to apply entire set, instead of 64 their relevant portion of patchset, please split the DTS patches into 65 separate patchset with a reference in changelog or cover letter to the 66 bindings submission on the mailing list. 67 68 8) If a documented compatible string is not yet matched by the 69 driver, the documentation should also include a compatible 70 string that is matched by the driver. 71 72 9) Bindings are actively used by multiple projects other than the Linux 73 Kernel, extra care and consideration may need to be taken when making changes 74 to existing bindings. 75 76II. For kernel maintainers 77========================== 78 79 1) If you aren't comfortable reviewing a given binding, reply to it and ask 80 the devicetree maintainers for guidance. This will help them prioritize 81 which ones to review and which ones are ok to let go. 82 83 2) For driver (not subsystem) bindings: If you are comfortable with the 84 binding, and it hasn't received an Acked-by from the devicetree 85 maintainers after a few weeks, go ahead and take it. 86 87 For subsystem bindings (anything affecting more than a single device), 88 getting a devicetree maintainer to review it is required. 89 90 3) For a series going though multiple trees, the binding patch should be 91 kept with the driver using the binding. 92 93 4) The DTS files should however never be applied via driver subsystem tree, 94 but always via platform SoC trees on dedicated branches (see also 95 Documentation/process/maintainer-soc.rst). 96 97III. Notes 98========== 99 100 0) Please see Documentation/devicetree/bindings/ABI.rst for details 101 regarding devicetree ABI. 102 103 1) This document is intended as a general familiarization with the process as 104 decided at the 2013 Kernel Summit. When in doubt, the current word of the 105 devicetree maintainers overrules this document. In that situation, a patch 106 updating this document would be appreciated. 107