General adr description

adr/readme.md

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+# Architecture Decision Records
+
+This directory contains Architecture Decision Records (ADRs) used throughout the OTA Reference Design.
+
+Unlike ADRs maintained within a single commercial project, these documents are **not** a historical record of decisions made for one specific product.
+
+Instead, they serve as **reference architectural decisions** illustrating how an experienced engineer might reason about common OTA design problems under different technical constraints.
+
+## Purpose
+
+Each ADR documents:
+
+- the engineering context;
+- the decision being considered;
+- the factors driving that decision;
+- the expected consequences;
+- the situations where the decision is appropriate;
+- the situations where another approach may be preferable.
+
+The goal is not to declare one solution universally correct.
+
+The goal is to explain **why** a particular decision would be reasonable for a particular class of systems.
+
+## Relationship to the Documentation
+
+The repository intentionally separates three different types of documents.
+
+### Concept Articles (`docs/`)
+
+Concept articles explain the design space.
+
+They answer questions such as:
+
+- What approaches exist?
+- How do they work?
+- What problems do they solve?
+- What trade-offs do they introduce?
+
+Their purpose is education.
+
+### Architecture Decision Records (`adr/`)
+
+ADRs answer a different question:
+
+> Given a particular set of engineering constraints, what decision would be made, and why?
+
+They intentionally focus on architectural reasoning rather than implementation details.
+
+### Decision Matrix
+
+After the individual ADRs, the series concludes with a decision matrix that compares the approaches and helps relate system constraints to architectural choices.
+
+The matrix is not intended to automatically select a solution. Instead, it provides a structured way to evaluate trade-offs.
+
+## Educational Nature
+
+These ADRs are examples.
+
+A real product may reach different conclusions depending on its:
+
+- reliability requirements;
+- hardware architecture;
+- network constraints;
+- operational model;
+- regulatory requirements;
+- maintenance strategy;
+- business priorities.
+
+For that reason, every ADR should be read as:
+
+> "Given these assumptions, this is the architectural decision we would make."
+
+rather than:
+
+> "This is the only correct solution."
+
+## Design Philosophy
+
+Throughout this repository, architectural decisions follow the same principle:
+
+> **Architecture should be driven by system constraints, not by technology preferences.**
+
+The objective is to teach the engineering process behind OTA design rather than promote a specific framework, product, or update mechanism.