[PATCH v2] Documentation/process: add soc maintainer handbook

[Bagas Sanjaya]

On Tue, May 30, 2023 at 01:49:36PM +0100, Conor Dooley wrote:
> diff --git a/Documentation/process/maintainer-soc.rst b/Documentation/process/maintainer-soc.rst
> new file mode 100644
> index 000000000000..9683c7d199b2
> --- /dev/null
> +++ b/Documentation/process/maintainer-soc.rst
> @@ -0,0 +1,178 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +.. _maintainer-soc:
> +
> +=============
> +SoC Subsystem
> +=============
> +
> +Overview
> +--------
> +
> +The SoC subsystem is a place of aggregation for SoC-specific code.
> +The main components of the subsystem are:
> +
> +* devicetrees for 32- & 64-bit ARM and RISC-V
> +* 32-bit ARM board files (arch/arm/mach*)
> +* 32- & 64-bit ARM defconfigs
> +* SoC specific drivers across architectures, in particular for 32- & 64-bit
> +  ARM, RISC-V and Loongarch
> +
> +These "SoC specific drivers" do not include clock, GPIO etc drivers that have
> +other top-level maintainers. The drivers/soc/ directory is generally meant
> +for kernel-internal drivers that are used by other drivers to provide SoC
> +specific functionality like identifying a SoC revision or interfacing with
> +power domains.
> +
> +The SoC subsystem also serves as an intermediate location for changes to
> +drivers/bus, drivers/firmware, drivers/reset and drivers/memory.  The addition
> +of new platforms, or the removal of existing ones, often go through the SoC
> +tree as a dedicated branch covering multiple subsystems.
> +
> +The main SoC tree is housed on git.kernel.org:
> +  https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git/
> +
> +Clearly this is quite a wide range of topics, which no one person, or even
> +small group of people are capable of maintaining.  Instead, the SoC subsystem
> +is comprised of many submaintainers, each taking care of individual platforms
> +and driver sub-directories.
> +In this regard, "platform" usually refers to a series of SoCs from a given
> +vendor, for example, Nvidia's series of Tegra SoCs.  Many submaintainers operate
> +on a vendor level, responsible for multiple product lines.  For several reasons,
> +including acquisitions/different business units in a company, things vary
> +significantly here.  The various submaintainers are documented in the
> +MAINTAINERS file.
> +
> +Most of these submaintainers have their own trees where they stage patches,
> +sending pull requests to the main SoC tree.  These trees are usually, but not
> +always, listed in MAINTAINERS.  The main SoC maintainers can be reached via the
> +alias soc at kernel.org if there is no platform-specific maintainer, or if they
> +are unresponsive.
> +
> +What the SoC tree is not, however, is a location for architecture specific code
> +changes.  Each architecture has it's own maintainers that are responsible for
> +architectural details, cpu errata and the like.
> +
> +Information for (new) Submaintainers
> +------------------------------------
> +
> +As new platforms spring up, they often bring with them new submaintainers,
> +many of whom work for the silicon vendor, and may not be familiar with the
> +process.
> +
> +Devicetree ABI Stability
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Perhaps one of the most important things to highlight is that dt-bindings
> +document the ABI between the devicetree and the kernel. Please see
> +:ref:`devicetree-abi` more information on the ABI.
> +
> +If changes are being made to a devicetree that are incompatible with old
> +kernels, the devicetree patch should not be applied until the driver is, or an
Until the incompatible driver changes are merged?
> +appropriate time later.  Most importantly, any incompatible changes should be
> +clearly pointed out in the patch description and pull request, along with the
> +expected impact on existing users, such as bootloaders or other operating
> +systems.
> +
> +Driver Branch Dependencies
> +~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +A common problem is synchronizing changes between device drivers and devicetree
> +files, even if a change is compatible in both directions, this may require
> +coordinating how the changes get merged through different maintainer trees.
> +
> +Usually the branch that includes a driver change will also include the
> +corresponding change to the devicetree binding description, to ensure they are
> +in fact compatible.  This means that the devicetree branch can end up causing
> +warnings in the "make dtbs_check" step.  If a devicetree change depends on
> +missing additions to a header file in include/dt-bindings/, it will fail the
> +"make dtbs" step and not get merged.

Sounds like passing `make dtbs` is a merging requirement.

> +Pull requests for bugfixes for the current release can be sent at any time, but
> +again having multiple smaller branches is better than trying to combine too many
> +patches into one pull request.
> +
> +The subject line of a pull request should begin with "[GIT PULL]" and made using
> +a signed tag, rather than a branch.  This tag should contain a short description
> +summarising the changes in the pull request.  For more detail on sending pull
> +requests, please see :ref:`pullrequests`.

As jon had said, I simply prefer to write the last cross-ref as:

```
... For more details on sending pull requests, see Documentation/maintainer/pull-requests.rst.
```

Thanks.

-- 
An old man doll... just what I always wanted! - Clara
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