add vendors.md doc about what it means to support opentelemetry

specification/vendors.md

@@ -0,0 +1,51 @@
+# Vendors
+
+<details>
+<summary>Table of Contents</summary>
+
+* [Abstract](#abstract)
+* [What it means to support OpenTelemetry](#what-it-means-to-support-opentelemetry)
+
+</details>
+
+## Abstract
+
+The OpenTelemetry project consists of both a
+[specification](https://github.com/open-telemetry/opentelemetry-specification)
+for the API, SDK, protocol and semantic conventions, as well as an
+implementation of each for a number of languages. The default SDK implementation
+is [highly configurable](sdk-configuration.md) and extendable, for example
+through [Span Processors](trace/sdk.md#span-processor), to allow for additional
+logic needed by particular vendors to be added without having to implement a
+custom SDK. By not requiring a custom SDK means for most languages a user will
+already find an implementation to use and if not they'll have a well documented
+specification to follow for implementing in a new language.
+
+The goal is for users to be able to easily switch between vendors while also
+ensuring that any language with an OpenTelemetry SDK implementation is able to
+work with any vendor who claims support for OpenTelemetry.
+
+This document will explain what is required of a vendor to be considered to
+"Support OpenTelemetry" or "Implements OpenTelemetry".
+
+## What it means to support OpenTelemetry
+
+## Tracing, Metrics and Logging Qualifications
+
+A vendor can qualify their support for OpenTelemetry with the type of telemetry
+they support. For example, a vendor that accepts the OpenTelemetry protocol
+exports for metrics only will be listed as "Supports OpenTelemetry Metrics".
+
+### Default SDK and the OpenTelemetry Protocol
+
+"Supports OpenTelemetry" means the vendor must accept the output of the default
+SDK through the OpenTelemetry Protocol either directly -- meaning the vendor's
+endpoint/collector/agent implements the receiver end of the protocol -- or as an
+exporter that works with the [OpenTelemetry
+Collector](https://github.com/open-telemetry/opentelemetry-collector/).
+
+### Custom SDK
+
+A vendor with a custom SDK implementation will be listed as "Implements
+OpenTelemetry". If the custom SDK is optional then the vendor can be listed as
+"Supports OpenTelemetry".