docs: add FAQ page (#2561)

* add FAQ

* lint

* remove section

Author: kayx23

docs/en/latest/FAQ.md

@@ -0,0 +1,56 @@
+---
+title: FAQ
+keywords:
+- APISIX Ingress
+- Apache APISIX
+- Kubernetes Ingress
+- Gateway API
+- FAQ
+description: This document provides answers to frequently asked questions (FAQ) when using APISIX Ingress Controller.
+---
+
+<!--
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+-->
+
+This document provides answers to frequently asked questions (FAQ) when using APISIX Ingress Controller.
+
+### How does Ingress Controller handle route priority across multiple resources?
+
+In APISIX, a higher value indicates a higher route priority.
+
+* **Ingress:** Does not support explicit route priority. Routes created using Ingress are assigned a default priority of 0, typically the lowest.
+* **HTTPRoute:** Has a [38-bit priority](https://github.com/apache/apisix-ingress-controller/blob/master/internal/adc/translator/httproute.go#L428-L448). The priority calculation is dynamic and may change, making exact values difficult to predict.
+* **APISIXRoute:** Can be assigned an explicit priority. To have a higher priority than an HTTPRoute, the value must exceed 549,755,813,887 (2^39 − 1).
+
+### How do HTTPRoute filters interact with PluginConfig CRDs?
+
+APISIX maps built-in Gateway API HTTPRoute filters to specific plugins:
+
+* `RequestHeaderModifier` → `proxy-rewrite`
+* `RequestRedirect` → `redirect`
+* `RequestMirror` → `proxy-mirror`
+* `URLRewrite` → `proxy-rewrite`
+* `ResponseHeaderModifier` → `response-rewrite`
+* `CORS` → `cors`
+* `ExtensionRef` → user-defined plugin reference
+
+When both filters and a PluginConfig CRD are applied:
+
+* If filters are applied first, PluginConfig overrides any overlapping plugin settings.
+* If PluginConfig is applied first, filters merge with PluginConfig settings, and overlapping fields from filters take precedence.

docs/en/latest/config.json

@@ -45,6 +45,10 @@
             "type": "doc",
             "id": "upgrade-guide"
         },
+        {
+            "type": "doc",
+            "id": "FAQ"
+        },
         {
             "type": "link",
             "label": "CHANGELOG",