MAINTAINERS: Create dedicated entries for 3rd party toolchains

Fixes: #63738

Create dedicated entries for ARC MWDT, arm compiler 6, and one Api
toolchains.

This helps contributors to identify whom to contact in case of issues
related to those toolchains.

The Zephyr SDK, cross-compile, and other GCC based compilers are covered
as part of the general cmake/toolchain,compiler,linker,bintools entry in
the MAINTAINERS file.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

MAINTAINERS.yml

@@ -2795,7 +2795,7 @@ TF-M Integration:
   labels:
     - "area: TF-M"
 
-Toolchain Integration:
+"Toolchain Integration":
   status: maintained
   maintainers:
     - tejlmand
@@ -2809,6 +2809,40 @@ Toolchain Integration:
   labels:
     - "area: Toolchains"
 
+"Toolchain ARC MWDT":
+  status: maintained
+  maintainers:
+    - evgeniy-paltsev
+    - abrodkin
+  files:
+    - cmake/*/arcmwdt/
+    - include/zephyr/toolchain/mwdt.h
+    - lib/libc/arcmwdt/*
+  labels:
+    - "area: Toolchains"
+
+"Toolchain arm compiler 6":
+  status: maintained
+  maintainers:
+    - tejlmand
+  files:
+    - cmake/*/armclang/
+    - cmake/linker/armlink/
+    - include/zephyr/toolchain/armclang.h
+    - lib/libc/armstdc/*
+  labels:
+    - "area: Toolchains"
+
+"Toolchain oneApi":
+  status: maintained
+  maintainers:
+    - nashif
+  files:
+    - cmake/*/oneApi/
+    - cmake/compiler/icx/
+  labels:
+    - "area: Toolchains"
+
 Tracing:
   status: maintained
   maintainers: