doc: add otlp ingestion endpoint to http api reference

docs/sources/reference/loki-http-api.md

@@ -24,6 +24,7 @@ Authorization needs to be done separately, for example, using an open-source loa
 These endpoints are exposed by the `distributor`, `write`, and `all` components:
 
 - [`POST /loki/api/v1/push`](#ingest-logs)
+- [`POST /otlp/v1/logs`](#ingest-logs-using-otlp)
 
 A [list of clients]({{< relref "../send-data" >}}) can be found in the clients documentation.
 
@@ -260,6 +261,15 @@ curl -H "Content-Type: application/json" \
   --data-raw '{"streams": [{ "stream": { "foo": "bar2" }, "values": [ [ "1570818238000000000", "fizzbuzz" ] ] }]}'
 ```
 
+## Ingest logs using OTLP
+
+```bash
+POST /otlp/v1/logs
+```
+
+`/otlp/v1/logs` allows OpenTelemetry Collector to send logs using `otlphttp` procotol into Loki. 
+Please refer to the [specific section]({{< relref "../send-data/otel" >}}) on how to configure.
+
 ## Query logs at a single point in time
 
 ```bash