README: restructure with role-based documentation and guidelines

Reorganize README to provide targeted documentation paths for different user
roles including developers, researchers, security experts, and maintainers.

Add quick start section and essential docs links.

Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20251121180009.2634393-1-sashal@kernel.org>

README

@@ -1,18 +1,156 @@
 Linux kernel
 ============
 
-There are several guides for kernel developers and users. These guides can
-be rendered in a number of formats, like HTML and PDF. Please read
-Documentation/admin-guide/README.rst first.
+The Linux kernel is the core of any Linux operating system. It manages hardware,
+system resources, and provides the fundamental services for all other software.
 
-In order to build the documentation, use ``make htmldocs`` or
-``make pdfdocs``.  The formatted documentation can also be read online at:
+Quick Start
+-----------
 
+* Report a bug: See Documentation/admin-guide/reporting-issues.rst
+* Get the latest kernel: https://kernel.org
+* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
+* Join the community: https://lore.kernel.org/
+
+Essential Documentation
+-----------------------
+
+All users should be familiar with:
+
+* Building requirements: Documentation/process/changes.rst
+* Code of Conduct: Documentation/process/code-of-conduct.rst
+* License: See COPYING
+
+Documentation can be built with make htmldocs or viewed online at:
 https://www.kernel.org/doc/html/latest/
 
-There are various text files in the Documentation/ subdirectory,
-several of them using the reStructuredText markup notation.
 
-Please read the Documentation/process/changes.rst file, as it contains the
-requirements for building and running the kernel, and information about
-the problems which may result by upgrading your kernel.
+Who Are You?
+============
+
+Find your role below:
+
+* New Kernel Developer - Getting started with kernel development
+* Academic Researcher - Studying kernel internals and architecture
+* Security Expert - Hardening and vulnerability analysis
+* Backport/Maintenance Engineer - Maintaining stable kernels
+* System Administrator - Configuring and troubleshooting
+* Maintainer - Leading subsystems and reviewing patches
+* Hardware Vendor - Writing drivers for new hardware
+* Distribution Maintainer - Packaging kernels for distros
+
+
+For Specific Users
+==================
+
+New Kernel Developer
+--------------------
+
+Welcome! Start your kernel development journey here:
+
+* Getting Started: Documentation/process/development-process.rst
+* Your First Patch: Documentation/process/submitting-patches.rst
+* Coding Style: Documentation/process/coding-style.rst
+* Build System: Documentation/kbuild/index.rst
+* Development Tools: Documentation/dev-tools/index.rst
+* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
+* Core APIs: Documentation/core-api/index.rst
+
+Academic Researcher
+-------------------
+
+Explore the kernel's architecture and internals:
+
+* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
+* Memory Management: Documentation/mm/index.rst
+* Scheduler: Documentation/scheduler/index.rst
+* Networking Stack: Documentation/networking/index.rst
+* Filesystems: Documentation/filesystems/index.rst
+* RCU (Read-Copy Update): Documentation/RCU/index.rst
+* Locking Primitives: Documentation/locking/index.rst
+* Power Management: Documentation/power/index.rst
+
+Security Expert
+---------------
+
+Security documentation and hardening guides:
+
+* Security Documentation: Documentation/security/index.rst
+* LSM Development: Documentation/security/lsm-development.rst
+* Self Protection: Documentation/security/self-protection.rst
+* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
+* CVE Procedures: Documentation/process/cve.rst
+* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
+* Security Features: Documentation/userspace-api/seccomp_filter.rst
+
+Backport/Maintenance Engineer
+-----------------------------
+
+Maintain and stabilize kernel versions:
+
+* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
+* Backporting Guide: Documentation/process/backporting.rst
+* Applying Patches: Documentation/process/applying-patches.rst
+* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
+* Git for Maintainers: Documentation/maintainer/configure-git.rst
+
+System Administrator
+--------------------
+
+Configure, tune, and troubleshoot Linux systems:
+
+* Admin Guide: Documentation/admin-guide/index.rst
+* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
+* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
+* Tracing/Debugging: Documentation/trace/index.rst
+* Performance Security: Documentation/admin-guide/perf-security.rst
+* Hardware Monitoring: Documentation/hwmon/index.rst
+
+Maintainer
+----------
+
+Lead kernel subsystems and manage contributions:
+
+* Maintainer Handbook: Documentation/maintainer/index.rst
+* Pull Requests: Documentation/maintainer/pull-requests.rst
+* Managing Patches: Documentation/maintainer/modifying-patches.rst
+* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
+* Development Process: Documentation/process/maintainer-handbooks.rst
+* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
+* Git Configuration: Documentation/maintainer/configure-git.rst
+
+Hardware Vendor
+---------------
+
+Write drivers and support new hardware:
+
+* Driver API Guide: Documentation/driver-api/index.rst
+* Driver Model: Documentation/driver-api/driver-model/driver.rst
+* Device Drivers: Documentation/driver-api/infrastructure.rst
+* Bus Types: Documentation/driver-api/driver-model/bus.rst
+* Device Tree Bindings: Documentation/devicetree/bindings/
+* Power Management: Documentation/driver-api/pm/index.rst
+* DMA API: Documentation/core-api/dma-api.rst
+
+Distribution Maintainer
+-----------------------
+
+Package and distribute the kernel:
+
+* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
+* ABI Documentation: Documentation/ABI/README
+* Kernel Configuration: Documentation/kbuild/kconfig.rst
+* Module Signing: Documentation/admin-guide/module-signing.rst
+* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
+* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst
+
+
+
+Communication and Support
+=========================
+
+* Mailing Lists: https://lore.kernel.org/
+* IRC: #kernelnewbies on irc.oftc.net
+* Bugzilla: https://bugzilla.kernel.org/
+* MAINTAINERS file: Lists subsystem maintainers and mailing lists
+* Email Clients: Documentation/process/email-clients.rst