docs: update otlp ingestion with correct endpoint and add endpoint to reference api docs (#12996)

Author: vitoorgomes

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 +261,16 @@ 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` lets the OpenTelemetry Collector send logs to Loki using `otlphttp` procotol.
+
+For information on how to configure Loki, refer to the [OTel Collector topic](https://grafana.com/docs/loki/<LOKI_VERSION>/send-data/otel/).
+
 ## Query logs at a single point in time
 
 ```bash

docs/sources/send-data/otel/_index.md

@@ -30,7 +30,7 @@ You need to make the following changes to the [OpenTelemetry Collector config](h
 ```yaml
 exporters:
   otlphttp:
-    endpoint: http://<loki-addr>:3100/otlp
+    endpoint: http://<loki-addr>:3100/otlp/v1/logs
 ```
 
 And enable it in `service.pipelines`:
@@ -57,7 +57,7 @@ exporters:
   otlphttp:
     auth:
       authenticator: basicauth/otlp
-    endpoint: http://<loki-addr>:3100/otlp
+    endpoint: http://<loki-addr>:3100/otlp/v1/logs
 
 service:
   extensions: [basicauth/otlp]