docs: Adding notes on how the process isolation works in HandBrake.

source/docs/en/latest/table-of-contents.markdown

@@ -128,6 +128,8 @@ Table of contents
   *Technical summary of the official presets*
 - [Performance](technical/performance.html)
   *How various settings affect encoding speed*
+- [Process Isolation](technical/process-isolation.html)
+  *Process Isolation and Multiple Simultaneous Jobs supports*
 - Video
   - [Video codecs](technical/video-codecs.html)<span class="notice draft"><span>draft</span></span>
   - [10/12-bit encoding](technical/video-bit-depth.html)<span class="notice draft"><span>draft</span></span>

source/docs/en/latest/technical/process-isolation.markdown

@@ -0,0 +1,67 @@
+---
+Type:            article
+Title:           Process Isolation
+Project:         HandBrake
+Project_URL:     https://handbrake.fr/
+Project_Version: Latest
+Language:        English
+Language_Code:   en
+Authors:         [ Scott (s55) ]
+Copyright:       2021 HandBrake Team
+License:         Creative Commons Attribution-ShareAlike 4.0 International
+License_Abbr:    CC BY-SA 4.0
+License_URL:     https://handbrake.fr/docs/license.html
+---
+
+Process Isolation
+============
+
+## What is Process isolation? 
+
+When HandBrake runs an encode, it now does so in a separate process. 
+This means that should an encode crash, the UI will remain responsive and continue processing the rest of the queue.
+
+This also allows us to run multiple encodes at the same time where your hardware can support it. 
+
+
+## Support
+
+This feature applies to the HandBrake GUI only.
+
+| UI        | Process Isolation | Multiple Simultaneous Encodes | Comments |
+|-----------|:-----------------:|:-----------------------------:|----------|
+| Windows   |   ✓               |   ✓                           |          |
+| macOS     |   ✓               |   ✓                           |          |
+| Linux     |                   |                               | Not currently supported. Possible for future release |
+
+
+Please note, to have multiple simultaneous jobs running you must have high end hardware. Typically you are going to want to have an 8-core CPU or better.
+Some hardware encoders do also support this but varies between 1 to 3 maximum jobs.
+
+
+## Settings for Process Isolation
+
+<!-- .system-macos -->
+Process Isolation can not be turned off. 
+
+In macOS, you can define the number of simultaneous jobs only.
+
+To control this behaviour see: HandBrake Menu -> Preferences -> Advanced
+
+<!-- /.system-macos -->
+
+<!-- .system-windows -->
+On Windows, HandBrake uses a separate process that will show up in task manager as "HandBrake.worker.exe"
+Please note, that this uses a small web server bound to 127.0.0.1.  As such, you may be alerted to the fact that HandBrake is making a connection to this process by your firewall. 
+This webserver can not be accessed remotely by any other machine on the local network. 
+This could potentially be an issue for some users, as such, we've provided additional controls for this functionality. 
+
+To control this behaviour see:  Tools Menu -> Preferences -> Advanced -> Process Isolation.
+
+Here you can enable / disable the feature, set the default port and set the number of simultaneous jobs.
+
+If you are using Portable HandBrake and want to completely disable this feature, you can do so by setting the portable.ini file to include the following line:
+
+    process.isolation.enabled = false
+
+<!-- /.system-windows -->