Doc reorg2 (#1189)

* doc_reorg2 updated TOC

* doc_reorg2 updates

* fix conflicts, add grid

docs/reference/API_Reference_Guide.rst

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+.. meta::
+  :description: Composable Kernel documentation and API reference library
+  :keywords: composable kernel, CK, ROCm, API, documentation
+
+.. _api-reference:
+
+********************************************************************
+API reference guide
+********************************************************************
+
+
+This document contains details of the APIs for the Composable Kernel (CK) library and introduces
+some of the key design principles that are used to write new classes that extend CK functionality.
+
+=================
+Using CK API
+=================
+
+This section describes how to use the CK library API.
+
+=================
+CK Datatypes
+=================
+
+-----------------
+DeviceMem
+-----------------
+
+.. doxygenstruct:: DeviceMem
+
+---------------------------
+Kernels For Flashattention
+---------------------------
+
+The Flashattention algorithm is defined in :cite:t:`dao2022flashattention`. This section lists
+the classes that are used in the CK GPU implementation of Flashattention.
+
+**Gridwise classes**
+
+.. doxygenstruct:: ck::GridwiseBatchedGemmSoftmaxGemm_Xdl_CShuffle
+
+**Blockwise classes**
+
+.. doxygenstruct:: ck::ThreadGroupTensorSliceTransfer_v4r1
+
+.. doxygenstruct:: ck::BlockwiseGemmXdlops_v2
+
+.. doxygenstruct:: ck::BlockwiseSoftmax
+
+**Threadwise classes**
+
+.. doxygenstruct:: ck::ThreadwiseTensorSliceTransfer_StaticToStatic
+
+.. bibliography::