Documentation/process/howto: Update for 4.x -> 5.x versioning

As linux-5.0 is coming up soon, the howto.rst document can be
updated for the new kernel version. Instead of changing all 4.x
references to 5.x, this time we git rid of all explicit version
numbers and rework some kernel trees' name to keep the docs
current and real.

Signed-off-by: Zenghui Yu <zenghuiyu96@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/howto.rst

@@ -235,22 +235,21 @@ Linux kernel development process currently consists of a few different
 main kernel "branches" and lots of different subsystem-specific kernel
 branches.  These different branches are:
 
-  - main 4.x kernel tree
-  - 4.x.y -stable kernel tree
-  - subsystem specific kernel trees and patches
-  - the 4.x -next kernel tree for integration tests
+  - Linus's mainline tree
+  - Various stable trees with multiple major numbers
+  - Subsystem-specific trees
+  - linux-next integration testing tree
 
-4.x kernel tree
-~~~~~~~~~~~~~~~
+Mainline tree
+~~~~~~~~~~~~~
 
-4.x kernels are maintained by Linus Torvalds, and can be found on
-https://kernel.org in the pub/linux/kernel/v4.x/ directory.  Its development
-process is as follows:
+Mainline tree are maintained by Linus Torvalds, and can be found at
+https://kernel.org or in the repo.  Its development process is as follows:
 
   - As soon as a new kernel is released a two weeks window is open,
     during this period of time maintainers can submit big diffs to
     Linus, usually the patches that have already been included in the
-    -next kernel for a few weeks.  The preferred way to submit big changes
+    linux-next for a few weeks.  The preferred way to submit big changes
     is using git (the kernel's source management tool, more information
     can be found at https://git-scm.com/) but plain patches are also just
     fine.
@@ -277,21 +276,19 @@ mailing list about kernel releases:
 	released according to perceived bug status, not according to a
 	preconceived timeline."*
 
-4.x.y -stable kernel tree
-~~~~~~~~~~~~~~~~~~~~~~~~~
+Various stable trees with multiple major numbers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Kernels with 3-part versions are -stable kernels. They contain
 relatively small and critical fixes for security problems or significant
-regressions discovered in a given 4.x kernel.
+regressions discovered in a given major mainline release, with the first
+2-part of version number are the same correspondingly.
 
 This is the recommended branch for users who want the most recent stable
 kernel and are not interested in helping test development/experimental
 versions.
 
-If no 4.x.y kernel is available, then the highest numbered 4.x
-kernel is the current stable kernel.
-
-4.x.y are maintained by the "stable" team <stable@vger.kernel.org>, and
+Stable trees are maintained by the "stable" team <stable@vger.kernel.org>, and
 are released as needs dictate.  The normal release period is approximately
 two weeks, but it can be longer if there are no pressing problems.  A
 security-related problem, instead, can cause a release to happen almost
@@ -301,8 +298,8 @@ The file :ref:`Documentation/process/stable-kernel-rules.rst <stable_kernel_rule
 in the kernel tree documents what kinds of changes are acceptable for
 the -stable tree, and how the release process works.
 
-Subsystem Specific kernel trees and patches
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Subsystem-specific trees
+~~~~~~~~~~~~~~~~~~~~~~~~
 
 The maintainers of the various kernel subsystems --- and also many
 kernel subsystem developers --- expose their current state of
@@ -326,19 +323,19 @@ revisions to it, and maintainers can mark patches as under review,
 accepted, or rejected.  Most of these patchwork sites are listed at
 https://patchwork.kernel.org/.
 
-4.x -next kernel tree for integration tests
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+linux-next integration testing tree
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Before updates from subsystem trees are merged into the mainline 4.x
-tree, they need to be integration-tested.  For this purpose, a special
+Before updates from subsystem trees are merged into the mainline tree,
+they need to be integration-tested.  For this purpose, a special
 testing repository exists into which virtually all subsystem trees are
 pulled on an almost daily basis:
 
 	https://git.kernel.org/?p=linux/kernel/git/next/linux-next.git
 
-This way, the -next kernel gives a summary outlook onto what will be
+This way, the linux-next gives a summary outlook onto what will be
 expected to go into the mainline kernel at the next merge period.
-Adventurous testers are very welcome to runtime-test the -next kernel.
+Adventurous testers are very welcome to runtime-test the linux-next.
 
 
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