Add INVIOLABLES.txt file.

INVIOLABLES.txt

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+The Inviolable Principles of Nuttx
+==================================
+
+These are properties of NuttX that can be certain of for all time 
+
+Definition
+----------
+
+*in·vi·o·la·ble*
+/inˈvīələbəl/
+
+adjective
+adjective: inviolable
+
+    never to be broken, infringed, or dishonored.
+
+    "an inviolable rule of chastity"
+
+    synonyms:  inalienable, absolute, untouchable, unalterable,
+               unchallengeable, unbreakable, impregnable; sacrosanct,
+               sacred, holy, hallowed; rare intemerate
+
+    "the inviolable right to life"
+
+Source: Oxford Dictionary of the English Language
+
+Strict POSIX compliance
+-----------------------
+
+  o Strict conformance to the portable standard OS interface as defined at
+    OpenGroup.org.
+  o A deeply embedded system requires some special support.  Special
+    support must be minimized.
+  o The portable interface must never be compromised only for the sake of
+    expediency.
+  o Expediency or even improved performance are not justifications for
+    violation of the strict POSIX interface
+
+Modular Architecture
+--------------------
+
+  o The internal modular architecture of the OS must maintained.
+  o This means formalizing and documenting all internal interfaces (in the
+    porting guide), minimal use of global variables at the interface, and
+    only well defined functional interfaces.
+
+Clear, Consistent, Standardized Coding Style
+--------------------------------------------
+
+  o Strict conformance to the NuttX coding style.  No "revolutionary"
+    changes to the coding standard (but perhaps some "evolutionary"
+    changes).
+  o Personal or organizational preference is not a justification for a
+    coding style change.
+  o Nothing can come into NuttX that does not follow the coding standard.
+  o Expediency is not a justification for violating the coding standard.
+
+Open and Unencumbered License
+-----------------------------
+
+  o Currently BSD 3-clause or compatible:  BSD 3-clause with constraints,
+    BSD 3 and 4 clause, MIT, public domain
+  o Other unencumbered licenses such as Apache may be considered
+    NuttX will never be licensed under a restrictive, "Copyleft" license.
+
+All Users Matter
+----------------
+
+  o All support must apply equally to all supported platforms.  At present
+    this includes Linux, Windows MSYS, Windows Cygwin, Windows Unbuntu,
+    Windows native, macOS, Solaris, and FreeBSD.  No tool/environment
+    solutions will be considered that limit the usage of NuttX on any of
+    the supported platforms.
+  o Inclusive rather than exclusive
+  o Hobbyists are valued users of the OS including retro computing hobbyists
+    * and DIY “Maker” hobbyists.
+  o Supported toolchains:  GCC, Clang, SDCC, ZiLOG ZDS-II (c89), IAR. 
+    Others?
+  o No changes to build system should limit use of NuttX by any user.
+  o Simplifying things for one user does not justify excluding another user.
+  o We should seek to expand the the NuttX user base, not to limit it for
+    reasons of preference or priority.
+  o We must resist the pull to make NuttX into a Linux-only, GCC-only, and
+    ARM-only solution.
+
+NuttX Branding
+--------------
+
+  o The official name of authentic Nuttx will always be "NuttX"
+  o This name is trademarked and may not be used by other OSs or forks of
+    NuttX
+
+The Enemies
+===========
+
+No Short Cuts
+-------------
+
+  o Doing things the easy way instead of the correct way.
+  o Reducing effort at the expense of Quality, Portability, or
+    Consistency
+  o Focus on the values of the organization, not the values of the Open
+    Source project.  Need to support both.
+  o It takes work to support the Inviolables.  There are no shortcuts.
+
+Sometimes Code Duplication is OK
+--------------------------------
+
+  o Sometimes is better to duplicate some logic than to introduce coupling
+
+Keep the Big Picture
+--------------------
+
+  o Too much focus on solving the problem in hand, loss of the Big Picture
+  o Insufficient understanding of the architectural principles.
+
+Conform to Standards
+--------------------
+
+  o Changing things only to suite a personal or organizational preference
+  o Inflexibility, Inability to adapt
+  o Not Invented Here (NIH) syndrome