isar: Update CONTRIBUTING

This patch
 * adds CI tests launching procedure description
 * adds the section "Trunk based development guidelines"
 * updates maintainers contacts

Closes: #45
Signed-off-by: Baurzhan Ismagulov <ibr@ilbers.de>
Signed-off-by: Maxim Yu. Osipov <mosipov@ilbers.de>

CONTRIBUTING.md

@@ -21,6 +21,19 @@ All technical communication about Isar should take place on `isar-users`
 mailing list. Please be polite and respect opinions and contributions of
 others.
 
+## Trunk based development guidelines
+
+We adapt trunk based development technique
+
+* `master` is the main development branch and not a stable release.
+
+* `next` is a branch for CI (Continous Integration), testing and early feedback.
+
+* `next` is sync'ed with `master` once in about two weeks (or more often whenever appropriate).
+
+If a major problem exists in `master`, it will be handled with priority.
+If a major change has been recently merged into `next`,  allow time to collect feedback and resolve issues.
+Plan merges to `master` so that both fit the two-week window; short extensions should be an exception.
 
 ## Development
 
@@ -64,6 +77,35 @@ others.
 
    * Seemingly unaffected boards still build.
 
+   * It's highly suggested to test your patchset before submitting it to the mailing
+     by launching CI tests scripts. The procedure is described below:
+
+    First, run "fast" CI
+```
+     scripts/ci_build.sh -q -f
+     ...
+     source isar-init-build-env
+     scripts/vm_smoke_test -f
+```
+    Currently "fast" CI launches
+     * parallel cross build of QEMU arm/arm64/amd64 Debian stretch and Raspberry Pi 1 Raspbian stretch targets
+     * cross build of one of the supported boards which includes compilation of Linux kernel/U-Boot for it
+     * Launches login prompt check tests for built QEMU targets
+
+    Second, run standard CI
+```
+     scripts/ci_build.sh -q
+     ...
+     source isar-init-build-env
+     scripts/vm_smoke_test -q
+```
+    Currently standard CI launches
+     * parallel native build of QEMU arm/arm64/i386/amd64 Debian stretch/buster and Raspberry Pi 1 Raspbian stretch targets
+     * Launches login prompt check tests for built QEMU targets
+
+    Active developers may request from maintainers an account on isar-build.org
+    to analyze CI logs or to launch their own CI builds there.
+
 4. Structure patches logically, in small increments.
 
    * One separable fix / improvement / addition - one patch. Do not provide
@@ -143,7 +185,7 @@ others.
 
      * Check with your employer when not working on your own.
 
-   * Base patches on top of the lastest master.
+   * Base patches on top of the latest 'next' branch
 
    * Every file should carry the copyright and licensing information:
 
@@ -171,7 +213,7 @@ others.
 
 1. Patches are reviewed on the mailing list.
 
-   * At least by maintainters, but everyone is invited, so the process can be
+   * At least by maintainers, but everyone is invited, so the process can be
      recurrent.
 
    * Feedback has to consider design, functionality and style.
@@ -179,10 +221,13 @@ others.
    * Simpler and clearer code is preferred, even if the original code works
      fine.
 
-2. After the review, patches are applied to the testing branch and CI checks
-   are executed.
+2. After the review, patches are applied to the maintainers testing branch and
+   CI checks are executed.
+
+3. If CI tests are passed OK and no new comments have appeared,
+   the patches are merged into the `next` branch and later (normally in two weeks)
+   into `master`.
 
-3. If no new comments have appeared, the patches are merged to master branch.
 
 GitHub facilities other than issues are not used for the review process, so
 that people can follow all changes and related discussions at one stop, the
@@ -193,7 +238,7 @@ mailing list. This may change in the future.
 
 1. Maintainers:
 
-   * Alexander Smirnov <asmirnov@ilbers.de>
+   * Maxim Yu. Osipov <mosipov@ilbers.de>
 
    * Baurzhan Ismagulov <ibr@ilbers.de>